kernel/linux.git/include/linux/filter.h, branch v4.9.319

bpf: Prevent increasing bpf_jit_limit above max

2021-11-26T10:48:20+00:00

[ Upstream commit fadb7ff1a6c2c565af56b4aacdd086b067eed440 ] Restrict bpf_jit_limit to the maximum supported by the arch's JIT. Signed-off-by: Lorenz Bauer Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211014142554.53120-4-lmb@cloudflare.com Signed-off-by: Sasha Levin

bpf: fix bpf_jit_limit knob for PAGE_SIZE >= 64K

2019-08-25T08:51:50+00:00

[ Upstream commit fdadd04931c2d7cd294dc5b2b342863f94be53a3 ] Michael and Sandipan report: Commit ede95a63b5 introduced a bpf_jit_limit tuneable to limit BPF JIT allocations. At compile time it defaults to PAGE_SIZE * 40000, and is adjusted again at init time if MODULES_VADDR is defined. For ppc64 kernels, MODULES_VADDR isn't defined, so we're stuck with the compile-time default at boot-time, which is 0x9c400000 when using 64K page size. This overflows the signed 32-bit bpf_jit_limit value: root@ubuntu:/tmp# cat /proc/sys/net/core/bpf_jit_limit -1673527296 and can cause various unexpected failures throughout the network stack. In one case `strace dhclient eth0` reported: setsockopt(5, SOL_SOCKET, SO_ATTACH_FILTER, {len=11, filter=0x105dd27f8}, 16) = -1 ENOTSUPP (Unknown error 524) and similar failures can be seen with tools like tcpdump. This doesn't always reproduce however, and I'm not sure why. The more consistent failure I've seen is an Ubuntu 18.04 KVM guest booted on a POWER9 host would time out on systemd/netplan configuring a virtio-net NIC with no noticeable errors in the logs. Given this and also given that in near future some architectures like arm64 will have a custom area for BPF JIT image allocations we should get rid of the BPF_JIT_LIMIT_DEFAULT fallback / default entirely. For 4.21, we have an overridable bpf_jit_alloc_exec(), bpf_jit_free_exec() so therefore add another overridable bpf_jit_alloc_exec_limit() helper function which returns the possible size of the memory area for deriving the default heuristic in bpf_jit_charge_init(). Like bpf_jit_alloc_exec() and bpf_jit_free_exec(), the new bpf_jit_alloc_exec_limit() assumes that module_alloc() is the default JIT memory provider, and therefore in case archs implement their custom module_alloc() we use MODULES_{END,_VADDR} for limits and otherwise for vmalloc_exec() cases like on ppc64 we use VMALLOC_{END,_START}. Additionally, for archs supporting large page sizes, we should change the sysctl to be handled as long to not run into sysctl restrictions in future. Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations") Reported-by: Sandipan Das Reported-by: Michael Roth Signed-off-by: Daniel Borkmann Tested-by: Michael Roth Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin

bpf: add bpf_jit_limit knob to restrict unpriv allocations

2019-08-25T08:51:41+00:00

commit ede95a63b5e84ddeea6b0c473b36ab8bfd8c6ce3 upstream. Rick reported that the BPF JIT could potentially fill the entire module space with BPF programs from unprivileged users which would prevent later attempts to load normal kernel modules or privileged BPF programs, for example. If JIT was enabled but unsuccessful to generate the image, then before commit 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") we would always fall back to the BPF interpreter. Nowadays in the case where the CONFIG_BPF_JIT_ALWAYS_ON could be set, then the load will abort with a failure since the BPF interpreter was compiled out. Add a global limit and enforce it for unprivileged users such that in case of BPF interpreter compiled out we fail once the limit has been reached or we fall back to BPF interpreter earlier w/o using module mem if latter was compiled in. In a next step, fair share among unprivileged users can be resolved in particular for the case where we would fail hard once limit is reached. Fixes: 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") Fixes: 0a14842f5a3c ("net: filter: Just In Time compiler for x86-64") Co-Developed-by: Rick Edgecombe Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Cc: Eric Dumazet Cc: Jann Horn Cc: Kees Cook Cc: LKML Signed-off-by: Alexei Starovoitov [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

bpf: add BPF_CALL_x macros for declaring helpers

2016-09-10T02:36:04+00:00

This work adds BPF_CALL_() macros and converts all the eBPF helper functions to use them, in a similar fashion like we do with SYSCALL_DEFINE() macros that are used today. Motivation for this is to hide all the register handling and all necessary casts from the user, so that it is done automatically in the background when adding a BPF_CALL_() call. This makes current helpers easier to review, eases to write future helpers, avoids getting the casting mess wrong, and allows for extending all helpers at once (f.e. build time checks, etc). It also helps detecting more easily in code reviews that unused registers are not instrumented in the code by accident, breaking compatibility with existing programs. BPF_CALL_() internals are quite similar to SYSCALL_DEFINE() ones with some fundamental differences, for example, for generating the actual helper function that carries all u64 regs, we need to fill unused regs, so that we always end up with 5 u64 regs as an argument. I reviewed several 0-5 generated BPF_CALL_() variants of the .i results and they look all as expected. No sparse issue spotted. We let this also sit for a few days with Fengguang's kbuild test robot, and there were no issues seen. On s390, it barked on the "uses dynamic stack allocation" notice, which is an old one from bpf_perf_event_output{,_tp}() reappearing here due to the conversion to the call wrapper, just telling that the perf raw record/frag sits on stack (gcc with s390's -mwarn-dynamicstack), but that's all. Did various runtime tests and they were fine as well. All eBPF helpers are now converted to use these macros, getting rid of a good chunk of all the raw castings. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

bpf: add BPF_SIZEOF and BPF_FIELD_SIZEOF macros

2016-09-10T02:36:04+00:00

Add BPF_SIZEOF() and BPF_FIELD_SIZEOF() macros to improve the code a bit which otherwise often result in overly long bytes_to_bpf_size(sizeof()) and bytes_to_bpf_size(FIELD_SIZEOF()) lines. So place them into a macro helper instead. Moreover, we currently have a BUILD_BUG_ON(BPF_FIELD_SIZEOF()) check in convert_bpf_extensions(), but we should rather make that generic as well and add a BUILD_BUG_ON() test in all BPF_SIZEOF()/BPF_FIELD_SIZEOF() users to detect any rewriter size issues at compile time. Note, there are currently none, but we want to assert that it stays this way. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2016-07-24T04:53:32+00:00

Just several instances of overlapping changes. Signed-off-by: David S. Miller

bpf: add XDP prog type for early driver filter

2016-07-20T04:46:31+00:00

Add a new bpf prog type that is intended to run in early stages of the packet rx path. Only minimal packet metadata will be available, hence a new context type, struct xdp_md, is exposed to userspace. So far only expose the packet start and end pointers, and only in read mode. An XDP program must return one of the well known enum values, all other return codes are reserved for future use. Unfortunately, this restriction is hard to enforce at verification time, so take the approach of warning at runtime when such programs are encountered. Out of bounds return codes should alias to XDP_ABORTED. Signed-off-by: Brenden Blanco Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

rose: limit sk_filter trim to payload

2016-07-13T18:53:40+00:00

Sockets can have a filter program attached that drops or trims incoming packets based on the filter program return value. Rose requires data packets to have at least ROSE_MIN_LEN bytes. It verifies this on arrival in rose_route_frame and unconditionally pulls the bytes in rose_recvmsg. The filter can trim packets to below this value in-between, causing pull to fail, leaving the partial header at the time of skb_copy_datagram_msg. Place a lower bound on the size to which sk_filter may trim packets by introducing sk_filter_trim_cap and call this for rose packets. Signed-off-by: Willem de Bruijn Acked-by: Daniel Borkmann Signed-off-by: David S. Miller

bpf: add generic constant blinding for use in jits

2016-05-16T17:49:32+00:00

This work adds a generic facility for use from eBPF JIT compilers that allows for further hardening of JIT generated images through blinding constants. In response to the original work on BPF JIT spraying published by Keegan McAllister [1], most BPF JITs were changed to make images read-only and start at a randomized offset in the page, where the rest was filled with trap instructions. We have this nowadays in x86, arm, arm64 and s390 JIT compilers. Additionally, later work also made eBPF interpreter images read only for kernels supporting DEBUG_SET_MODULE_RONX, that is, x86, arm, arm64 and s390 archs as well currently. This is done by default for mentioned JITs when JITing is enabled. Furthermore, we had a generic and configurable constant blinding facility on our todo for quite some time now to further make spraying harder, and first implementation since around netconf 2016. We found that for systems where untrusted users can load cBPF/eBPF code where JIT is enabled, start offset randomization helps a bit to make jumps into crafted payload harder, but in case where larger programs that cross page boundary are injected, we again have some part of the program opcodes at a page start offset. With improved guessing and more reliable payload injection, chances can increase to jump into such payload. Elena Reshetova recently wrote a test case for it [2, 3]. Moreover, eBPF comes with 64 bit constants, which can leave some more room for payloads. Note that for all this, additional bugs in the kernel are still required to make the jump (and of course to guess right, to not jump into a trap) and naturally the JIT must be enabled, which is disabled by default. For helping mitigation, the general idea is to provide an option bpf_jit_harden that admins can tweak along with bpf_jit_enable, so that for cases where JIT should be enabled for performance reasons, the generated image can be further hardened with blinding constants for unpriviledged users (bpf_jit_harden == 1), with trading off performance for these, but not for privileged ones. We also added the option of blinding for all users (bpf_jit_harden == 2), which is quite helpful for testing f.e. with test_bpf.ko. There are no further e.g. hardening levels of bpf_jit_harden switch intended, rationale is to have it dead simple to use as on/off. Since this functionality would need to be duplicated over and over for JIT compilers to use, which are already complex enough, we provide a generic eBPF byte-code level based blinding implementation, which is then just transparently JITed. JIT compilers need to make only a few changes to integrate this facility and can be migrated one by one. This option is for eBPF JITs and will be used in x86, arm64, s390 without too much effort, and soon ppc64 JITs, thus that native eBPF can be blinded as well as cBPF to eBPF migrations, so that both can be covered with a single implementation. The rule for JITs is that bpf_jit_blind_constants() must be called from bpf_int_jit_compile(), and in case blinding is disabled, we follow normally with JITing the passed program. In case blinding is enabled and we fail during the process of blinding itself, we must return with the interpreter. Similarly, in case the JITing process after the blinding failed, we return normally to the interpreter with the non-blinded code. Meaning, interpreter doesn't change in any way and operates on eBPF code as usual. For doing this pre-JIT blinding step, we need to make use of a helper/auxiliary register, here BPF_REG_AX. This is strictly internal to the JIT and not in any way part of the eBPF architecture. Just like in the same way as JITs internally make use of some helper registers when emitting code, only that here the helper register is one abstraction level higher in eBPF bytecode, but nevertheless in JIT phase. That helper register is needed since f.e. manually written program can issue loads to all registers of eBPF architecture. The core concept with the additional register is: blind out all 32 and 64 bit constants by converting BPF_K based instructions into a small sequence from K_VAL into ((RND ^ K_VAL) ^ RND). Therefore, this is transformed into: BPF_REG_AX := (RND ^ K_VAL), BPF_REG_AX ^= RND, and REG BPF_REG_AX, so actual operation on the target register is translated from BPF_K into BPF_X one that is operating on BPF_REG_AX's content. During rewriting phase when blinding, RND is newly generated via prandom_u32() for each processed instruction. 64 bit loads are split into two 32 bit loads to make translation and patching not too complex. Only basic thing required by JITs is to call the helper bpf_jit_blind_constants()/bpf_jit_prog_release_other() pair, and to map BPF_REG_AX into an unused register. Small bpf_jit_disasm extract from [2] when applied to x86 JIT: echo 0 > /proc/sys/net/core/bpf_jit_harden ffffffffa034f5e9 + : [...] 39: mov $0xa8909090,%eax 3e: mov $0xa8909090,%eax 43: mov $0xa8ff3148,%eax 48: mov $0xa89081b4,%eax 4d: mov $0xa8900bb0,%eax 52: mov $0xa810e0c1,%eax 57: mov $0xa8908eb4,%eax 5c: mov $0xa89020b0,%eax [...] echo 1 > /proc/sys/net/core/bpf_jit_harden ffffffffa034f1e5 + : [...] 39: mov $0xe1192563,%r10d 3f: xor $0x4989b5f3,%r10d 46: mov %r10d,%eax 49: mov $0xb8296d93,%r10d 4f: xor $0x10b9fd03,%r10d 56: mov %r10d,%eax 59: mov $0x8c381146,%r10d 5f: xor $0x24c7200e,%r10d 66: mov %r10d,%eax 69: mov $0xeb2a830e,%r10d 6f: xor $0x43ba02ba,%r10d 76: mov %r10d,%eax 79: mov $0xd9730af,%r10d 7f: xor $0xa5073b1f,%r10d 86: mov %r10d,%eax 89: mov $0x9a45662b,%r10d 8f: xor $0x325586ea,%r10d 96: mov %r10d,%eax [...] As can be seen, original constants that carry payload are hidden when enabled, actual operations are transformed from constant-based to register-based ones, making jumps into constants ineffective. Above extract/example uses single BPF load instruction over and over, but of course all instructions with constants are blinded. Performance wise, JIT with blinding performs a bit slower than just JIT and faster than interpreter case. This is expected, since we still get all the performance benefits from JITing and in normal use-cases not every single instruction needs to be blinded. Summing up all 296 test cases averaged over multiple runs from test_bpf.ko suite, interpreter was 55% slower than JIT only and JIT with blinding was 8% slower than JIT only. Since there are also some extremes in the test suite, I expect for ordinary workloads that the performance for the JIT with blinding case is even closer to JIT only case, f.e. nmap test case from suite has averaged timings in ns 29 (JIT), 35 (+ blinding), and 151 (interpreter). BPF test suite, seccomp test suite, eBPF sample code and various bigger networking eBPF programs have been tested with this and were running fine. For testing purposes, I also adapted interpreter and redirected blinded eBPF image to interpreter and also here all tests pass. [1] http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.html [2] https://github.com/01org/jit-spray-poc-for-ksp/ [3] http://www.openwall.com/lists/kernel-hardening/2016/05/03/5 Signed-off-by: Daniel Borkmann Reviewed-by: Elena Reshetova Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

bpf: prepare bpf_int_jit_compile/bpf_prog_select_runtime apis

2016-05-16T17:49:32+00:00

Since the blinding is strictly only called from inside eBPF JITs, we need to change signatures for bpf_int_jit_compile() and bpf_prog_select_runtime() first in order to prepare that the eBPF program we're dealing with can change underneath. Hence, for call sites, we need to return the latest prog. No functional change in this patch. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller