* syzbot <syzbot+c0f0941337ade4c26ed1@xxxxxxxxxxxxxxxxxxxxxxxxx> [240719 16:01]: > Hello, > > syzbot found the following issue on: This bug doesn't exist anymore. > > HEAD commit: 3fe121b62282 Add linux-next specific files for 20240712 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=1769e695980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=98dd8c4bab5cdce > dashboard link: https://syzkaller.appspot.com/bug?extid=c0f0941337ade4c26ed1 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/8c6fbf69718d/disk-3fe121b6.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/39fc7e43dfc1/vmlinux-3fe121b6.xz > kernel image: https://storage.googleapis.com/syzbot-assets/0a78e70e4b4e/bzImage-3fe121b6.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+c0f0941337ade4c26ed1@xxxxxxxxxxxxxxxxxxxxxxxxx > > > ============================================ > WARNING: possible recursive locking detected > 6.10.0-rc7-next-20240712-syzkaller #0 Not tainted > -------------------------------------------- > mount/4518 is trying to acquire lock: > ffff88801d2b1498 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock+0x1c/0x60 include/linux/mmap_lock.h:144 > > but task is already holding lock: > ffff88801d2b1498 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:144 [inline] > ffff88801d2b1498 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x159/0xc80 mm/mmap.c:3396 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&mm->mmap_lock); > lock(&mm->mmap_lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 1 lock held by mount/4518: > #0: ffff88801d2b1498 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:144 [inline] > #0: ffff88801d2b1498 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x159/0xc80 mm/mmap.c:3396 > > stack backtrace: > CPU: 1 UID: 0 PID: 4518 Comm: mount Not tainted 6.10.0-rc7-next-20240712-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:94 [inline] > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 > print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3034 > check_deadlock kernel/locking/lockdep.c:3086 [inline] > validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3888 > __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199 > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822 > down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526 > mmap_read_lock+0x1c/0x60 include/linux/mmap_lock.h:144 > unmap_single_vma+0x2a0/0x330 mm/memory.c:1832 > unmap_vmas+0x3cc/0x5f0 mm/memory.c:1904 > exit_mmap+0x264/0xc80 mm/mmap.c:3412 > __mmput+0x115/0x390 kernel/fork.c:1347 > exit_mm+0x220/0x310 kernel/exit.c:571 This is discussed here [1]. There is some case where unmap_single_vma() was reached without the lock held in write mode and the flag seems to have been misunderstood. [1.] https://lore.kernel.org/all/20240710-bug12-v1-1-0e5440f9b8d3@xxxxxxxxx/ Thanks, Liam
