bc4fe4cdd6
The syzbot reported the below general protection fault: general protection fault, probably for non-canonical address 0xe00eeaee0000003b: 0000 [#1] PREEMPT SMP KASAN KASAN: maybe wild-memory-access in range [0x00777770000001d8-0x00777770000001df] CPU: 1 PID: 10488 Comm: syz-executor721 Not tainted 5.9.0-rc3-syzkaller #0 RIP: 0010:unlink_file_vma+0x57/0xb0 mm/mmap.c:164 Call Trace: free_pgtables+0x1b3/0x2f0 mm/memory.c:415 exit_mmap+0x2c0/0x530 mm/mmap.c:3184 __mmput+0x122/0x470 kernel/fork.c:1076 mmput+0x53/0x60 kernel/fork.c:1097 exit_mm kernel/exit.c:483 [inline] do_exit+0xa8b/0x29f0 kernel/exit.c:793 do_group_exit+0x125/0x310 kernel/exit.c:903 get_signal+0x428/0x1f00 kernel/signal.c:2757 arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811 exit_to_user_mode_loop kernel/entry/common.c:136 [inline] exit_to_user_mode_prepare+0x1ae/0x200 kernel/entry/common.c:167 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:242 entry_SYSCALL_64_after_hwframe+0x44/0xa9 It's because the ->mmap() callback can change vma->vm_file and fput the original file. But the commit d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") failed to catch this case and always fput() the original file, hence add an extra fput(). [ Thanks Hillf for pointing this extra fput() out. ] Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") Reported-by: syzbot+c5d5a51dcbb558ca0cb5@syzkaller.appspotmail.com Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Christian König <ckoenig.leichtzumerken@gmail.com> Cc: Hongxiang Lou <louhongxiang@huawei.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Dave Airlie <airlied@redhat.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: John Hubbard <jhubbard@nvidia.com> Link: https://lkml.kernel.org/r/20200916090733.31427-1-linmiaohe@huawei.com Signed-off-by: Linus Torvalds <torvalds@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.