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Conceptually, we want the memory mappings to always be up to date and
represent whatever is in the TLB. To ensure that, we need to sync them
over in the userspace case and for the kernel we need to process the
mappings.
The kernel will call flush_tlb_* if page table entries that were valid
before become invalid. Unfortunately, this is not the case if entries
are added.
As such, change both flush_tlb_* and set_ptes to track the memory range
that has to be synchronized. For the kernel, we need to execute a
flush_tlb_kern_* immediately but we can wait for the first page fault in
case of set_ptes. For userspace in contrast we only store that a range
of memory needs to be synced and do so whenever we switch to that
process.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-13-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The HVC update was mostly used to compress consecutive calls into one.
This is mostly relevant for userspace where it is already handled by the
syscall stub code.
Simplify the whole logic and consolidate it for both kernel and
userspace. This does remove the sequential syscall compression for the
kernel, however that shouldn't be the main factor in most runs.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-12-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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As running the syscalls is expensive due to context switches, we should
do so as late as possible in case more syscalls need to be queued later
on. This will also benefit a later move to a SECCOMP enabled userspace
as in that case the need for extra context switches is removed entirely.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-9-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The kernel flushes the memory ranges anyway for CoW and does not assume
that the userspace process has anything set up already. So, start with a
fresh process for the new mm context.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The current LDT code has a few issues that mean it should be redone in a
different way once we always start with a fresh MM even when cloning.
In a new and better world, the kernel would just ensure its own LDT is
clear at startup. At that point, all that is needed is a simple function
to populate the LDT from another MM in arch_dup_mmap combined with some
tracking of the installed LDT entries for each MM.
Note that the old implementation was even incorrect with regard to
reading, as it copied out the LDT entries in the internal format rather
than converting them to the userspace structure.
Removal should be fine as the LDT is not used for thread-local storage
anymore.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-7-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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To keep the number of syscalls that the stub has to do lower, compress
two consecutive syscalls of the same type if the second is just a
continuation of the first.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-6-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Rework syscall handling to be platform independent. Also create a clean
split between queueing of syscalls and flushing them out, removing the
need to keep state in the code that triggers the syscalls.
The code adds syscall_data_len to the global mm_id structure. This will
be used later to allow surrounding code to track whether syscalls still
need to run and if errors occurred.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When we switch to use seccomp, we need both the signal stack and other
data (i.e. syscall information) to co-exist in the stub data. To
facilitate this, start by defining separate memory areas for the stack
and syscall data.
This moves the signal stack onto a new page as the memory area is not
sufficient to hold both signal stack and syscall information.
Only change the signal stack setup for now, as the syscall code will be
reworked later.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When signals are hard-blocked in order to do time-travel
socket processing, we set signals_blocked and then handle
SIGIO signals by setting the SIGIO bit in signals_pending.
When unblocking, we first set signals_blocked to 0, and
then handle all pending signals. We have to set it first,
so that we can again properly block/unblock inside the
unblock, if the time-travel handlers need to be processed.
Unfortunately, this is racy. We can get into this situation:
// signals_pending = SIGIO_MASK
unblock_signals_hard()
signals_blocked = 0;
if (signals_pending && signals_enabled) {
block_signals();
unblock_signals()
...
sig_handler_common(SIGIO, NULL, NULL);
sigio_handler()
...
sigio_reg_handler()
irq_do_timetravel_handler()
reg->timetravel_handler() ==
vu_req_interrupt_comm_handler()
vu_req_read_message()
vhost_user_recv_req()
vhost_user_recv()
vhost_user_recv_header()
// reads 12 bytes header of
// 20 bytes message
<-- receive SIGIO here <--
sig_handler()
int enabled = signals_enabled; // 1
if ((signals_blocked || !enabled) && (sig == SIGIO)) {
if (!signals_blocked && time_travel_mode == TT_MODE_EXTERNAL)
sigio_run_timetravel_handlers()
_sigio_handler()
sigio_reg_handler()
... as above ...
vhost_user_recv_header()
// reads 8 bytes that were message payload
// as if it were header - but aborts since
// it then gets -EAGAIN
...
--> end signal handler -->
// continue in vhost_user_recv()
// full_read() for 8 bytes payload busy loops
// entire process hangs here
Conceptually, to fix this, we need to ensure that the
signal handler cannot run while we hard-unblock signals.
The thing that makes this more complex is that we can be
doing hard-block/unblock while unblocking. Introduce a
new signals_blocked_pending variable that we can keep at
non-zero as long as pending signals are being processed,
then we only need to ensure it's decremented safely and
the signal handler will only increment it if it's already
non-zero (or signals_blocked is set, of course.)
Note also that only the outermost call to hard-unblock is
allowed to decrement signals_blocked_pending, since it
could otherwise reach zero in an inner call, and leave
the same race happening if the timetravel_handler loops,
but that's basically required of it.
Fixes: d6b399a0e02a ("um: time-travel/signals: fix ndelay() in interrupt")
Link: https://patch.msgid.link/20240703110144.28034-2-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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For the upcoming shared-memory time-travel external
optimisations, we need to be able to mmap/mremap.
Add the necessary OS calls.
Link: https://patch.msgid.link/20240702192118.ca4472963638.Ic2da1d3a983fe57340c1b693badfa9c5bd2d8c61@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Change os_rcv_fd() to os_rcv_fd_msg() that can more generally
receive any number of FDs in any kind of message.
Link: https://patch.msgid.link/20240702192118.40b78b2bfe4e.Ic6ec12d72630e5bcae1e597d6bd5c6f29f441563@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Add a message type to the time-travel protocol to broadcast
a small (64-bit) value to all participants in a simulation.
The main use case is to have an identical message come to
all participants in a simulation, e.g. to separate out logs
for different tests running in a single simulation.
Down in the guts of time_travel_handle_message() we can't
use printk() and not even printk_deferred(), so just store
the message and print it at the start of the userspace()
function.
Unfortunately this means that other prints in the kernel
can actually bypass the message, but in most cases where
this is used, for example to separate test logs, userspace
will be involved. Also, even if we could use
printk_deferred(), we'd still need to flush it out in the
userspace() function since otherwise userspace messages
might cross it.
As a result, this is a reasonable compromise, there's no
need to have any core changes and it solves the main use
case we have for it.
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Link: https://patch.msgid.link/20240702192118.c4093bc5b15e.I2ca8d006b67feeb866ac2017af7b741c9e06445a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When in time-travel mode (infinite-cpu or external) time should not pass
for writing to the console. As such, it makes sense to put the FD for
the output side into blocking mode and simply let any write to it hang.
If we did not do this, then time could pass waiting for the console to
become writable again. This is not desirable as it has random effects on
the clock between runs.
Implement this by duplicating the FD if output is active in a relevant
mode and setting the duplicate to be blocking. This avoids changing the
input channel to be blocking should it exists. After this, use the
blocking FD for all write operations and do not allocate an IRQ it is
set.
Without time-travel mode fd_out will always match fd_in and IRQs are
registered.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20231018123643.1255813-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Move relevant declarations to this header. This will address
below -Wmissing-prototypes warnings:
arch/um/os-Linux/elf_aux.c:26:13: warning: no previous prototype for ‘scan_elf_aux’ [-Wmissing-prototypes]
arch/um/os-Linux/mem.c:213:13: warning: no previous prototype for ‘check_tmpexec’ [-Wmissing-prototypes]
arch/um/os-Linux/skas/process.c:107:6: warning: no previous prototype for ‘wait_stub_done’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Make it match its definition (size_t vs unsigned long). And declare
it in a shared header to fix the -Wmissing-prototypes warning, as it
is defined in the user code and called in the kernel code.
Fixes: 5b301409e8bc ("UML: add support for KASAN under x86_64")
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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These functions are not called explicitly. Let's just workaround
the -Wmissing-prototypes warnings by declaring them locally similar
to what was done in arch/x86/kernel/asm-offsets_32.c.
This will address below -Wmissing-prototypes warnings:
./arch/x86/um/shared/sysdep/kernel-offsets.h:9:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:187:7: warning: no previous prototype for ‘__wrap_malloc’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:208:7: warning: no previous prototype for ‘__wrap_calloc’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:222:6: warning: no previous prototype for ‘__wrap_free’ [-Wmissing-prototypes]
arch/x86/um/user-offsets.c:17:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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This will address below -Wmissing-prototypes warnings:
arch/um/kernel/initrd.c:18:12: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes]
arch/um/kernel/um_arch.c:408:19: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes]
arch/um/os-Linux/start_up.c:301:12: warning: no previous prototype for ‘parse_iomem’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:15:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:101:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:153:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_64.c:111:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_64.c:171:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes]
arch/x86/um/syscalls_64.c:48:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes]
arch/x86/um/tls_32.c:184:5: warning: no previous prototype for ‘arch_switch_tls’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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This will also fix the warnings like:
warning: no previous prototype for ‘fork_handler’ [-Wmissing-prototypes]
140 | void fork_handler(void)
| ^~~~~~~~~~~~
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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The ARCH=um build has its own idea about strscpy()'s definition. Adjust
the callers to remove the redundant sizeof() arguments ahead of treewide
changes, since it needs a manual adjustment for the newly named
sized_strscpy() export.
Cc: Richard Weinberger <richard@nod.at>
Cc: linux-um@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
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These functions were only used when calling PTRACE_ARCH_PRCTL, but this
code has been removed.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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The trampoline is running in a cloned process. It is not safe to use
printk for error printing there.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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The threads allocated inside the kernel have only a single page of
stack. Unfortunately, the vfprintf function in standard glibc may use
too much stack-space, overflowing it.
To make os_info safe to be used by helper threads, use the kernel
vscnprintf function into a smallish buffer and write out the information
to stderr.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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For the detection code to check whether SYSEMU_SINGLESTEP works
correctly we needed some error cases while stopping to be non-fatal.
However, at this point stop_ptraced_child must always succeed, and we
can therefore simplify it slightly to exit immediately on error.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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start_userspace is only called from exactly one location, and the passed
pointer for the userspace process stack cannot be NULL.
Remove the check, without changing the control flow.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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These features have existed since Linux 2.6.14 and can be considered
widely available at this point. Also drop the backward compatibility
code for PTRACE_SETOPTIONS.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
----
v2:
* Continue to define PTRACE_SYSEMU_SINGLESTEP as glibc only added it in
version 2.27.
Signed-off-by: Richard Weinberger <richard@nod.at>
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__cant_sleep was already used and exported by the scheduler.
The name had to be changed to a UML specific one.
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Reviewed-by: Peter Lafreniere <peter@n8pjl.ca>
Signed-off-by: Richard Weinberger <richard@nod.at>
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`strncpy` is deprecated for use on NUL-terminated destination strings [1].
`gate_buf` should always be NUL-terminated and does not require
NUL-padding. It is used as a string arg inside an argv array given to
`run_helper()`. Due to this, let's use `strscpy` as it guarantees
NUL-terminated on the destination buffer preventing potential buffer
overreads [2].
This exact invocation was changed from `strcpy` to `strncpy` in commit
7879b1d94badb ("um,ethertap: use strncpy") back in 2015. Let's continue
hardening our `str*cpy` apis and use the newer and safer `strscpy`!
Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230911-strncpy-arch-um-os-linux-drivers-ethertap_user-c-v1-1-d9e53f52ab32@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening updates from Kees Cook:
"As has become normal, changes are scattered around the tree (either
explicitly maintainer Acked or for trivial stuff that went ignored):
- Carve out the new CONFIG_LIST_HARDENED as a more focused subset of
CONFIG_DEBUG_LIST (Marco Elver)
- Fix kallsyms lookup failure under Clang LTO (Yonghong Song)
- Clarify documentation for CONFIG_UBSAN_TRAP (Jann Horn)
- Flexible array member conversion not carried in other tree (Gustavo
A. R. Silva)
- Various strlcpy() and strncpy() removals not carried in other trees
(Azeem Shaikh, Justin Stitt)
- Convert nsproxy.count to refcount_t (Elena Reshetova)
- Add handful of __counted_by annotations not carried in other trees,
as well as an LKDTM test
- Fix build failure with gcc-plugins on GCC 14+
- Fix selftests to respect SKIP for signal-delivery tests
- Fix CFI warning for paravirt callback prototype
- Clarify documentation for seq_show_option_n() usage"
* tag 'hardening-v6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (23 commits)
LoadPin: Annotate struct dm_verity_loadpin_trusted_root_digest with __counted_by
kallsyms: Change func signature for cleanup_symbol_name()
kallsyms: Fix kallsyms_selftest failure
nsproxy: Convert nsproxy.count to refcount_t
integrity: Annotate struct ima_rule_opt_list with __counted_by
lkdtm: Add FAM_BOUNDS test for __counted_by
Compiler Attributes: counted_by: Adjust name and identifier expansion
um: refactor deprecated strncpy to memcpy
um: vector: refactor deprecated strncpy
alpha: Replace one-element array with flexible-array member
hardening: Move BUG_ON_DATA_CORRUPTION to hardening options
list: Introduce CONFIG_LIST_HARDENED
list_debug: Introduce inline wrappers for debug checks
compiler_types: Introduce the Clang __preserve_most function attribute
gcc-plugins: Rename last_stmt() for GCC 14+
selftests/harness: Actually report SKIP for signal tests
x86/paravirt: Fix tlb_remove_table function callback prototype warning
EISA: Replace all non-returning strlcpy with strscpy
perf: Replace strlcpy with strscpy
um: Remove strlcpy declaration
...
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This reverts commit 9b0da3f22307af693be80f5d3a89dc4c7f360a85.
The sigio.c is clearly user space code which is handled by
arch/um/scripts/Makefile.rules (see USER_OBJS rule).
The above mentioned commit simply broke this agreement,
we may not use Linux kernel internal headers in them without
thorough thinking.
Hence, revert the wrong commit.
Link: https://lkml.kernel.org/r/20230724143131.30090-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307212304.cH79zJp1-lkp@intel.com/
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Herve Codina <herve.codina@bootlin.com>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Richard Weinberger <richard@nod.at>
Cc: Yang Guang <yang.guang5@zte.com.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230703160641.1790935-1-azeemshaikh38@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Remove the deprecated rule to build *.dtbo from *.dts
- Refactor section mismatch detection in modpost
- Fix bogus ARM section mismatch detections
- Fix error of 'make gtags' with O= option
- Add Clang's target triple to KBUILD_CPPFLAGS to fix a build error
with the latest LLVM version
- Rebuild the built-in initrd when KBUILD_BUILD_TIMESTAMP is changed
- Ignore more compiler-generated symbols for kallsyms
- Fix 'make local*config' to handle the ${CONFIG_FOO} form in Makefiles
- Enable more kernel-doc warnings with W=2
- Refactor <linux/export.h> by generating KSYMTAB data by modpost
- Deprecate <asm/export.h> and <asm-generic/export.h>
- Remove the EXPORT_DATA_SYMBOL macro
- Move the check for static EXPORT_SYMBOL back to modpost, which makes
the build faster
- Re-implement CONFIG_TRIM_UNUSED_KSYMS with one-pass algorithm
- Warn missing MODULE_DESCRIPTION when building modules with W=1
- Make 'make clean' robust against too long argument error
- Exclude more objects from GCOV to fix CFI failures with GCOV
- Allow 'make modules_install' to install modules.builtin and
modules.builtin.modinfo even when CONFIG_MODULES is disabled
- Include modules.builtin and modules.builtin.modinfo in the
linux-image Debian package even when CONFIG_MODULES is disabled
- Revive "Entering directory" logging for the latest Make version
* tag 'kbuild-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (72 commits)
modpost: define more R_ARM_* for old distributions
kbuild: revive "Entering directory" for Make >= 4.4.1
kbuild: set correct abs_srctree and abs_objtree for package builds
scripts/mksysmap: Ignore prefixed KCFI symbols
kbuild: deb-pkg: remove the CONFIG_MODULES check in buildeb
kbuild: builddeb: always make modules_install, to install modules.builtin*
modpost: continue even with unknown relocation type
modpost: factor out Elf_Sym pointer calculation to section_rel()
modpost: factor out inst location calculation to section_rel()
kbuild: Disable GCOV for *.mod.o
kbuild: Fix CFI failures with GCOV
kbuild: make clean rule robust against too long argument error
script: modpost: emit a warning when the description is missing
kbuild: make modules_install copy modules.builtin(.modinfo)
linux/export.h: rename 'sec' argument to 'license'
modpost: show offset from symbol for section mismatch warnings
modpost: merge two similar section mismatch warnings
kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion
modpost: use null string instead of NULL pointer for default namespace
modpost: squash sym_update_namespace() into sym_add_exported()
...
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strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230614003604.1021205-1-azeemshaikh38@gmail.com
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This reverts commit cead61a6717a9873426b08d73a34a325e3546f5d.
It exported __stack_smash_handler and __guard, while they may not be
defined by anyone.
The code *declares* __stack_smash_handler and __guard. It does not
create weak symbols. If no external library is linked, they are left
undefined, but yet exported.
If a loadable module tries to access non-existing symbols, bad things
(a page fault, NULL pointer dereference, etc.) will happen. So, the
current code is wrong and dangerous.
If the code were written as follows, it would *define* them as weak
symbols so modules would be able to get access to them.
void (*__stack_smash_handler)(void *) __attribute__((weak));
EXPORT_SYMBOL(__stack_smash_handler);
long __guard __attribute__((weak));
EXPORT_SYMBOL(__guard);
In fact, modpost forbids exporting undefined symbols. It shows an error
message if it detects such a mistake.
ERROR: modpost: "..." [...] was exported without definition
Unfortunately, it is checked only when the code is built as modular.
The problem described above has been unnoticed for a long time because
arch/um/os-Linux/user_syms.c is always built-in.
With a planned change in Kbuild, exporting undefined symbols will always
result in a build error instead of a run-time error. It is a good thing,
but we need to fix the breakage in advance.
One fix is to define weak symbols as shown above. An alternative is to
export them conditionally as follows:
#ifdef CONFIG_STACKPROTECTOR
extern void __stack_smash_handler(void *);
EXPORT_SYMBOL(__stack_smash_handler);
external long __guard;
EXPORT_SYMBOL(__guard);
#endif
This is what other architectures do; EXPORT_SYMBOL(__stack_chk_guard)
is guarded by #ifdef CONFIG_STACKPROTECTOR.
However, adding the #ifdef guard is not sensible because UML cannot
enable the stack-protector in the first place! (Please note UML does
not select HAVE_STACKPROTECTOR in Kconfig.)
So, the code is already broken (and unused) in multiple ways.
Just remove.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux
Pull uml updates from Richard Weinberger:
- Make stub data pages configurable
- Make it harder to mix user and kernel code by accident
* tag 'uml-for-linus-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
um: make stub data pages size tweakable
um: prevent user code in modules
um: further clean up user_syms
um: don't export printf()
um: hostfs: define our own API boundary
um: add __weak for exported functions
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There's a lot of code here that hard-codes that the
data is a single page, and right now that seems to
be sufficient, but to make it easier to change this
in the future, add a new STUB_DATA_PAGES constant
and use it throughout the code.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Make some cleanups, add and fix some comments and document
here that we shouldn't export (libc) symbols for "_user.c"
code, rather such should work like hostfs does now.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Since printf() cannot be used in kernel threads (it
uses too much stack space) don't export it for modules
either.
This should leave us exporting only things that are
absolutely critical (such as memset and friends) and
things that are injected by the compiler (stack guard
and similar.)
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Instead of exporting the set of functions provided by
glibc that are needed for hostfs_user.c, just build that
into the kernel image whenever hostfs is built, and then
export _those_ functions cleanly, to be independent of
the libc implementation.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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If the exported glibc functions don't exist, we get link
failures. Avoid that by adding __weak so they're allowed
to not exist.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
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ELF is acronym and therefore should be spelled in all caps.
I left one exception at Documentation/arm/nwfpe/nwfpe.rst which looks like
being written in the first person.
Link: https://lkml.kernel.org/r/Y/3wGWQviIOkyLJW@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux
Pull UML updates from Richard Weinberger:
- Add support for rust (yay!)
- Add support for LTO
- Add platform bus support to virtio-pci
- Various virtio fixes
- Coding style, spelling cleanups
* tag 'uml-for-linus-6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux: (27 commits)
Documentation: rust: Fix arch support table
uml: vector: Remove unused definitions VECTOR_{WRITE,HEADERS}
um: virt-pci: properly remove PCI device from bus
um: virtio_uml: move device breaking into workqueue
um: virtio_uml: mark device as unregistered when breaking it
um: virtio_uml: free command if adding to virtqueue failed
UML: define RUNTIME_DISCARD_EXIT
virt-pci: add platform bus support
um-virt-pci: Make max delay configurable
um: virt-pci: implement pcibios_get_phb_of_node()
um: Support LTO
um: put power options in a menu
um: Use CFLAGS_vmlinux
um: Prevent building modules incompatible with MODVERSIONS
um: Avoid pcap multiple definition errors
um: Make the definition of cpu_data more compatible
x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list
rust: arch/um: Add support for CONFIG_RUST under x86_64 UML
rust: arch/um: Disable FP/SIMD instruction to match x86
rust: arch/um: Use 'pie' relocation mode under UML
...
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I added $(srctree)/ to some included Makefiles in the following commits:
- 3204a7fb98a3 ("kbuild: prefix $(srctree)/ to some included Makefiles")
- d82856395505 ("kbuild: do not require sub-make for separate output tree builds")
They were a preparation for removing --include-dir flag.
I have never thought --include-dir useful. Rather, it _is_ harmful.
For example, run the following commands:
$ make -s ARCH=x86 mrproper defconfig
$ make ARCH=arm O=foo dtbs
make[1]: Entering directory '/tmp/linux/foo'
HOSTCC scripts/basic/fixdep
Error: kernelrelease not valid - run 'make prepare' to update it
UPD include/config/kernel.release
make[1]: Leaving directory '/tmp/linux/foo'
The first command configures the source tree for x86. The next command
tries to build ARM device trees in the separate foo/ directory - this
must stop because the directory foo/ has not been configured yet.
However, due to --include-dir=$(abs_srctree), the top Makefile includes
the wrong include/config/auto.conf from the source tree and continues
building. Kbuild traverses the directory tree, but of course it does
not work correctly. The Error message is also pointless - 'make prepare'
does not help at all for fixing the issue.
This commit fixes more arch Makefile, and finally removes --include-dir
from the top Makefile.
There are more breakages under drivers/, but I do not volunteer to fix
them all. I just moved --include-dir to drivers/Makefile.
With this commit, the second command will stop with a sensible message.
$ make -s ARCH=x86 mrproper defconfig
$ make ARCH=arm O=foo dtbs
make[1]: Entering directory '/tmp/linux/foo'
SYNC include/config/auto.conf.cmd
***
*** The source tree is not clean, please run 'make ARCH=arm mrproper'
*** in /tmp/linux
***
make[2]: *** [../Makefile:646: outputmakefile] Error 1
/tmp/linux/Makefile:770: include/config/auto.conf.cmd: No such file or directory
make[1]: *** [/tmp/linux/Makefile:793: include/config/auto.conf.cmd] Error 2
make[1]: Leaving directory '/tmp/linux/foo'
make: *** [Makefile:226: __sub-make] Error 2
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This means having the string literal in one line and using __func__
where appropriate.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Return the value epoll_ctl() directly instead of storing it in another
redundant variable.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Enable FORTIFY_SOURCE so running Kunit tests can test fortified
functions.
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: David Gow <davidgow@google.com>
Link: https://lore.kernel.org/r/20220210003224.773957-1-keescook@chromium.org
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git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml
Pull UML updates from Richard Weinberger:
- KASAN support for x86_64
- noreboot command line option, just like qemu's -no-reboot
- Various fixes and cleanups
* tag 'for-linus-5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
um: include sys/types.h for size_t
um: Replace to_phys() and to_virt() with less generic function names
um: Add missing apply_returns()
um: add "noreboot" command line option for PANIC_TIMEOUT=-1 setups
um: include linux/stddef.h for __always_inline
UML: add support for KASAN under x86_64
mm: Add PAGE_ALIGN_DOWN macro
um: random: Don't initialise hwrng struct with zero
um: remove unused mm_copy_segments
um: remove unused variable
um: Remove straying parenthesis
um: x86: print RIP with symbol
arch: um: Fix build for statically linked UML w/ constructors
x86/um: Kconfig: Fix indentation
um/drivers: Kconfig: Fix indentation
um: Kconfig: Fix indentation
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UML generally does not provide access to special CPU instructions like
RDRAND, and execution tends to be rather deterministic, with no real
hardware interrupts, making good randomness really very hard, if not
all together impossible. Not only is this a security eyebrow raiser, but
it's also quite annoying when trying to do various pieces of UML-based
automation that takes a long time to boot, if ever.
Fix this by trivially calling getrandom() in the host and using that
seed as "bootloader randomness", which initializes the rng immediately
at UML boot.
The old behavior can be restored the same way as on any other arch, by
way of CONFIG_TRUST_BOOTLOADER_RANDOMNESS=n or
random.trust_bootloader=0. So seen from that perspective, this just
makes UML act like other archs, which is positive in its own right.
Additionally, wire up arch_get_random_{int,long}() in the same way, so
that reseeds can also make use of the host RNG, controllable by
CONFIG_TRUST_CPU_RANDOMNESS and random.trust_cpu, per usual.
Cc: stable@vger.kernel.org
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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to_virt() and to_phys() are very generic and may be defined by drivers.
As it turns out, commit 9409c9b6709e ("pmem: refactor pmem_clear_poison()")
did exactly that. This results in build errors such as the following
when trying to build um:allmodconfig.
drivers/nvdimm/pmem.c: In function ‘pmem_dax_zero_page_range’:
./arch/um/include/asm/page.h:105:20: error:
too few arguments to function ‘to_phys’
105 | #define __pa(virt) to_phys((void *) (unsigned long) (virt))
| ^~~~~~~
Use less generic function names for the um specific to_phys() and to_virt()
functions to fix the problem and to avoid similar problems in the future.
Fixes: 9409c9b6709e ("pmem: refactor pmem_clear_poison()")
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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QEMU has a -no-reboot option, which halts instead of reboots when the
guest asks to reboot. This is invaluable when used with
CONFIG_PANIC_TIMEOUT=-1 (and panic_on_warn), because it allows panics
and warnings to be caught immediately in CI. Implement this in UML too,
by way of a basic setup param.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Make KASAN run on User Mode Linux on x86_64.
The UML-specific KASAN initializer uses mmap to map the ~16TB of shadow
memory to the location defined by KASAN_SHADOW_OFFSET. kasan_init()
utilizes constructors to initialize KASAN before main().
The location of the KASAN shadow memory, starting at
KASAN_SHADOW_OFFSET, can be configured using the KASAN_SHADOW_OFFSET
option. The default location of this offset is 0x100000000000, which
keeps it out-of-the-way even on UML setups with more "physical" memory.
For low-memory setups, 0x7fff8000 can be used instead, which fits in an
immediate and is therefore faster, as suggested by Dmitry Vyukov. There
is usually enough free space at this location; however, it is a config
option so that it can be easily changed if needed.
Note that, unlike KASAN on other architectures, vmalloc allocations
still use the shadow memory allocated upfront, rather than allocating
and free-ing it per-vmalloc allocation.
If another architecture chooses to go down the same path, we should
replace the checks for CONFIG_UML with something more generic, such
as:
- A CONFIG_KASAN_NO_SHADOW_ALLOC option, which architectures could set
- or, a way of having architecture-specific versions of these vmalloc
and module shadow memory allocation options.
Also note that, while UML supports both KASAN in inline mode
(CONFIG_KASAN_INLINE) and static linking (CONFIG_STATIC_LINK), it does
not support both at the same time.
Signed-off-by: Patricia Alfonso <trishalfonso@google.com>
Co-developed-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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