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syzbot found the following crash: BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13 Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173 CPU: 0 PID: 26173 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #146 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13 trace_lock_acquire include/trace/events/lock.h:13 [inline] lock_acquire+0x2de/0x410 kernel/locking/lockdep.c:4411 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] shmem_fault+0x5ec/0x7b0 mm/shmem.c:2034 __do_fault+0x111/0x540 mm/memory.c:3083 do_shared_fault mm/memory.c:3535 [inline] do_fault mm/memory.c:3613 [inline] handle_pte_fault mm/memory.c:3840 [inline] __handle_mm_fault+0x2adf/0x3f20 mm/memory.c:3964 handle_mm_fault+0x1b5/0x6b0 mm/memory.c:4001 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline] __do_page_fault+0x536/0xdd0 arch/x86/mm/fault.c:1506 do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530 page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1202 It happens if the VMA got unmapped under us while we dropped mmap_sem and inode got freed. Pinning the file if we drop mmap_sem fixes the issue. Link: http://lkml.kernel.org/r/20190927083908.rhifa4mmaxefc24r@box Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: syzbot+03ee87124ee05af991bd@syzkaller.appspotmail.com Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Hillf Danton <hdanton@sina.com> Cc: Hugh Dickins <hughd@google.com> Cc: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 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.