BMC/Intel-BMC/linux.git/fs/binfmt_elf.c, branch dev-5.10-intel

fs: Replace zero-length array with flexible-array member

2020-10-29T22:22:59+00:00

There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays Signed-off-by: Gustavo A. R. Silva

binfmt_elf: take the mmap lock around find_extend_vma()

2020-10-18T16:27:09+00:00

create_elf_tables() runs after setup_new_exec(), so other tasks can already access our new mm and do things like process_madvise() on it. (At the time I'm writing this commit, process_madvise() is not in mainline yet, but has been in akpm's tree for some time.) While I believe that there are currently no APIs that would actually allow another process to mess up our VMA tree (process_madvise() is limited to MADV_COLD and MADV_PAGEOUT, and uring and userfaultfd cannot reach an mm under which no syscalls have been executed yet), this seems like an accident waiting to happen. Let's make sure that we always take the mmap lock around GUP paths as long as another process might be able to see the mm. (Yes, this diff looks suspicious because we drop the lock before doing anything with `vma`, but that's because we actually don't do anything with it apart from the NULL check.) Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Acked-by: Michel Lespinasse Cc: "Eric W . Biederman" Cc: Jason Gunthorpe Cc: John Hubbard Cc: Mauro Carvalho Chehab Cc: Sakari Ailus Link: https://lkml.kernel.org/r/CAG48ez1-PBCdv3y8pn-Ty-b+FmBSLwDuVKFSt8h7wARLy0dF-Q@mail.gmail.com Signed-off-by: Linus Torvalds

binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot

2020-10-16T18:11:21+00:00

In both binfmt_elf and binfmt_elf_fdpic, use a new helper dump_vma_snapshot() to take a snapshot of the VMA list (including the gate VMA, if we have one) while protected by the mmap_lock, and then use that snapshot instead of walking the VMA list without locking. An alternative approach would be to keep the mmap_lock held across the entire core dumping operation; however, keeping the mmap_lock locked while we may be blocked for an unbounded amount of time (e.g. because we're dumping to a FUSE filesystem or so) isn't really optimal; the mmap_lock blocks things like the ->release handler of userfaultfd, and we don't really want critical system daemons to grind to a halt just because someone "gifted" them SCM_RIGHTS to an eternally-locked userfaultfd, or something like that. Since both the normal ELF code and the FDPIC ELF code need this functionality (and if any other binfmt wants to add coredump support in the future, they'd probably need it, too), implement this with a common helper in fs/coredump.c. A downside of this approach is that we now need a bigger amount of kernel memory per userspace VMA in the normal ELF case, and that we need O(n) kernel memory in the FDPIC ELF case at all; but 40 bytes per VMA shouldn't be terribly bad. There currently is a data race between stack expansion and anything that reads ->vm_start or ->vm_end under the mmap_lock held in read mode; to mitigate that for core dumping, take the mmap_lock in write mode when taking a snapshot of the VMA hierarchy. (If we only took the mmap_lock in read mode, we could end up with a corrupted core dump if someone does get_user_pages_remote() concurrently. Not really a major problem, but taking the mmap_lock either way works here, so we might as well avoid the issue.) (This doesn't do anything about the existing data races with stack expansion in other mm code.) Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Acked-by: Linus Torvalds Cc: Christoph Hellwig Cc: Alexander Viro Cc: "Eric W . Biederman" Cc: Oleg Nesterov Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20200827114932.3572699-6-jannh@google.com Signed-off-by: Linus Torvalds

coredump: rework elf/elf_fdpic vma_dump_size() into common helper

2020-10-16T18:11:21+00:00

At the moment, the binfmt_elf and binfmt_elf_fdpic code have slightly different code to figure out which VMAs should be dumped, and if so, whether the dump should contain the entire VMA or just its first page. Eliminate duplicate code by reworking the binfmt_elf version into a generic core dumping helper in coredump.c. As part of that, change the heuristic for detecting executable/library header pages to check whether the inode is executable instead of looking at the file mode. This is less problematic in terms of locking because it lets us avoid get_user() under the mmap_sem. (And arguably it looks nicer and makes more sense in generic code.) Adjust a little bit based on the binfmt_elf_fdpic version: ->anon_vma is only meaningful under CONFIG_MMU, otherwise we have to assume that the VMA has been written to. Suggested-by: Linus Torvalds Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Acked-by: Linus Torvalds Cc: Christoph Hellwig Cc: Alexander Viro Cc: "Eric W . Biederman" Cc: Oleg Nesterov Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20200827114932.3572699-5-jannh@google.com Signed-off-by: Linus Torvalds

coredump: refactor page range dumping into common helper

2020-10-16T18:11:21+00:00

Both fs/binfmt_elf.c and fs/binfmt_elf_fdpic.c need to dump ranges of pages into the coredump file. Extract that logic into a common helper. Signed-off-by: Jann Horn Signed-off-by: Andrew Morton Acked-by: Linus Torvalds Cc: Christoph Hellwig Cc: Alexander Viro Cc: "Eric W . Biederman" Cc: Oleg Nesterov Cc: Hugh Dickins Link: http://lkml.kernel.org/r/20200827114932.3572699-4-jannh@google.com Signed-off-by: Linus Torvalds

fs/binfmt_elf: use PT_LOAD p_align values for suitable start address

2020-10-16T18:11:21+00:00

Patch series "Selecting Load Addresses According to p_align", v3. The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. While specifying -z,max-page-size=0x200000 to the linker will generate suitably aligned segments for huge pages on x86_64, the executable needs to be loaded at a suitably aligned address as well. This alignment requires the binary's cooperation, as distinct segments need to be appropriately paddded to be eligible for THP. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. This patch (of 2): The current ELF loading mechancism provides page-aligned mappings. This can lead to the program being loaded in a way unsuitable for file-backed, transparent huge pages when handling PIE executables. For binaries built with increased alignment, this limits the number of bits usable for ASLR, but provides some randomization over using fixed load addresses/non-PIE binaries. Tested by verifying program with -Wl,-z,max-page-size=0x200000 loading. [akpm@linux-foundation.org: fix max() warning] [ckennelly@google.com: augment comment] Link: https://lkml.kernel.org/r/20200821233848.3904680-2-ckennelly@google.com Signed-off-by: Chris Kennelly Signed-off-by: Andrew Morton Cc: Alexander Viro Cc: Alexey Dobriyan Cc: Song Liu Cc: David Rientjes Cc: Ian Rogers Cc: Hugh Dickens Cc: Suren Baghdasaryan Cc: Sandeep Patil Cc: Fangrui Song Cc: Nick Desaulniers Cc: "Kirill A. Shutemov" Cc: Mike Kravetz Cc: Shuah Khan Link: https://lkml.kernel.org/r/20200820170541.1132271-1-ckennelly@google.com Link: https://lkml.kernel.org/r/20200820170541.1132271-2-ckennelly@google.com Signed-off-by: Linus Torvalds

kill elf_fpxregs_t

2020-07-27T18:29:23+00:00

all uses are conditional upon ELF_CORE_COPY_XFPREGS, which has not been defined on any architecture since 2010 Signed-off-by: Al Viro

introduction of regset ->get() wrappers, switching ELF coredumps to those

2020-07-27T18:24:50+00:00

Two new helpers: given a process and regset, dump into a buffer. regset_get() takes a buffer and size, regset_get_alloc() takes size and allocates a buffer. Return value in both cases is the amount of data actually dumped in case of success or -E... on error. In both cases the size is capped by regset->n * regset->size, so ->get() is called with offset 0 and size no more than what regset expects. binfmt_elf.c callers of ->get() are switched to using those; the other caller (copy_regset_to_user()) will need some preparations to switch. Signed-off-by: Al Viro

Merge branch 'uaccess.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2020-06-10T23:02:54+00:00

Pull misc uaccess updates from Al Viro: "Assorted uaccess patches for this cycle - the stuff that didn't fit into thematic series" * 'uaccess.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: bpf: make bpf_check_uarg_tail_zero() use check_zeroed_user() x86: kvm_hv_set_msr(): use __put_user() instead of 32bit __clear_user() user_regset_copyout_zero(): use clear_user() TEST_ACCESS_OK _never_ had been checked anywhere x86: switch cp_stat64() to unsafe_put_user() binfmt_flat: don't use __put_user() binfmt_elf_fdpic: don't use __... uaccess primitives binfmt_elf: don't bother with __{put,copy_to}_user() pselect6() and friends: take handling the combined 6th/7th args into helper

Merge branch 'akpm' (patches from Andrew)

2020-06-05T02:18:29+00:00

Merge yet more updates from Andrew Morton: - More MM work. 100ish more to go. Mike Rapoport's "mm: remove __ARCH_HAS_5LEVEL_HACK" series should fix the current ppc issue - Various other little subsystems * emailed patches from Andrew Morton : (127 commits) lib/ubsan.c: fix gcc-10 warnings tools/testing/selftests/vm: remove duplicate headers selftests: vm: pkeys: fix multilib builds for x86 selftests: vm: pkeys: use the correct page size on powerpc selftests/vm/pkeys: override access right definitions on powerpc selftests/vm/pkeys: test correct behaviour of pkey-0 selftests/vm/pkeys: introduce a sub-page allocator selftests/vm/pkeys: detect write violation on a mapped access-denied-key page selftests/vm/pkeys: associate key on a mapped page and detect write violation selftests/vm/pkeys: associate key on a mapped page and detect access violation selftests/vm/pkeys: improve checks to determine pkey support selftests/vm/pkeys: fix assertion in test_pkey_alloc_exhaust() selftests/vm/pkeys: fix number of reserved powerpc pkeys selftests/vm/pkeys: introduce powerpc support selftests/vm/pkeys: introduce generic pkey abstractions selftests: vm: pkeys: use the correct huge page size selftests/vm/pkeys: fix alloc_random_pkey() to make it really random selftests/vm/pkeys: fix assertion in pkey_disable_set/clear() selftests/vm/pkeys: fix pkey_disable_clear() selftests: vm: pkeys: add helpers for pkey bits ...