187da0f825
The routine __vma_private_lock tests for the existence of a reserve map associated with a private hugetlb mapping. A pointer to the reserve map is in vma->vm_private_data. __vma_private_lock was checking the pointer for NULL. However, it is possible that the low bits of the pointer could be used as flags. In such instances, vm_private_data is not NULL and not a valid pointer. This results in the null-ptr-deref reported by syzbot: general protection fault, probably for non-canonical address 0xdffffc000000001d: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef] CPU: 0 PID: 5048 Comm: syz-executor139 Not tainted 6.6.0-rc7-syzkaller-00142-g88 8cf78c29e2 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 1 0/09/2023 RIP: 0010:__lock_acquire+0x109/0x5de0 kernel/locking/lockdep.c:5004 ... Call Trace: <TASK> lock_acquire kernel/locking/lockdep.c:5753 [inline] lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718 down_write+0x93/0x200 kernel/locking/rwsem.c:1573 hugetlb_vma_lock_write mm/hugetlb.c:300 [inline] hugetlb_vma_lock_write+0xae/0x100 mm/hugetlb.c:291 __hugetlb_zap_begin+0x1e9/0x2b0 mm/hugetlb.c:5447 hugetlb_zap_begin include/linux/hugetlb.h:258 [inline] unmap_vmas+0x2f4/0x470 mm/memory.c:1733 exit_mmap+0x1ad/0xa60 mm/mmap.c:3230 __mmput+0x12a/0x4d0 kernel/fork.c:1349 mmput+0x62/0x70 kernel/fork.c:1371 exit_mm kernel/exit.c:567 [inline] do_exit+0x9ad/0x2a20 kernel/exit.c:861 __do_sys_exit kernel/exit.c:991 [inline] __se_sys_exit kernel/exit.c:989 [inline] __x64_sys_exit+0x42/0x50 kernel/exit.c:989 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd Mask off low bit flags before checking for NULL pointer. In addition, the reserve map only 'belongs' to the OWNER (parent in parent/child relationships) so also check for the OWNER flag. Link: https://lkml.kernel.org/r/20231114012033.259600-1-mike.kravetz@oracle.com Reported-by: syzbot+6ada951e7c0f7bc8a71e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/00000000000078d1e00608d7878b@google.com/ Fixes: bf4916922c60 ("hugetlbfs: extend hugetlb_vma_lock to private VMAs") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Rik van Riel <riel@surriel.com> Cc: Edward Adam Davis <eadavis@qq.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Tom Rix <trix@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.