On Wed, Jan 10, 2018 at 7:58 AM, syzbot <syzbot+8ec30bb7bf1a981a2012@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > Hello, > > syzkaller hit the following crash on > d476c5334f1dee122534b29639f8d46a85ecbb9d > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. > C reproducer is attached > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > for information about syzkaller reproducers I think this is drivers/staging/android/ashmem.c, +android maintainers. > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+8ec30bb7bf1a981a2012@xxxxxxxxxxxxxxxxxxxxxxxxx > It will help syzbot understand when the bug is fixed. See footer for > details. > If you forward the report, please keep this part and the footer. > > > ====================================================== > audit: type=1400 audit(1515535006.781:8): avc: denied { map } for > pid=3497 comm="syzkaller303685" path="/dev/ashmem" dev="devtmpfs" ino=178 > scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 > tcontext=system_u:object_r:device_t:s0 tclass=chr_file permissive=1 > WARNING: possible circular locking dependency detected > 4.15.0-rc7+ #255 Not tainted > ------------------------------------------------------ > syzkaller303685/3497 is trying to acquire lock: > (&sb->s_type->i_mutex_key#11){++++}, at: [<000000006886b3fb>] inode_lock > include/linux/fs.h:713 [inline] > (&sb->s_type->i_mutex_key#11){++++}, at: [<000000006886b3fb>] > shmem_file_llseek+0xef/0x240 mm/shmem.c:2579 > > but task is already holding lock: > (ashmem_mutex){+.+.}, at: [<00000000a44304a8>] ashmem_llseek+0x56/0x1f0 > drivers/staging/android/ashmem.c:334 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #2 (ashmem_mutex){+.+.}: > __mutex_lock_common kernel/locking/mutex.c:756 [inline] > __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 > mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 > ashmem_mmap+0x53/0x410 drivers/staging/android/ashmem.c:370 > call_mmap include/linux/fs.h:1777 [inline] > mmap_region+0xa99/0x15a0 mm/mmap.c:1705 > do_mmap+0x6c0/0xe00 mm/mmap.c:1483 > do_mmap_pgoff include/linux/mm.h:2217 [inline] > vm_mmap_pgoff+0x1de/0x280 mm/util.c:333 > SYSC_mmap_pgoff mm/mmap.c:1533 [inline] > SyS_mmap_pgoff+0x462/0x5f0 mm/mmap.c:1491 > SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] > SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91 > entry_SYSCALL_64_fastpath+0x23/0x9a > > -> #1 (&mm->mmap_sem){++++}: > __might_fault+0x13a/0x1d0 mm/memory.c:4529 > _copy_to_user+0x2c/0xc0 lib/usercopy.c:25 > copy_to_user include/linux/uaccess.h:155 [inline] > filldir+0x1a7/0x320 fs/readdir.c:196 > dir_emit_dot include/linux/fs.h:3374 [inline] > dir_emit_dots include/linux/fs.h:3385 [inline] > dcache_readdir+0x12d/0x5e0 fs/libfs.c:192 > iterate_dir+0x1ca/0x530 fs/readdir.c:51 > SYSC_getdents fs/readdir.c:231 [inline] > SyS_getdents+0x225/0x450 fs/readdir.c:212 > entry_SYSCALL_64_fastpath+0x23/0x9a > > -> #0 (&sb->s_type->i_mutex_key#11){++++}: > lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914 > down_write+0x87/0x120 kernel/locking/rwsem.c:70 > inode_lock include/linux/fs.h:713 [inline] > shmem_file_llseek+0xef/0x240 mm/shmem.c:2579 > vfs_llseek+0xa2/0xd0 fs/read_write.c:300 > ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:346 > vfs_llseek fs/read_write.c:300 [inline] > SYSC_lseek fs/read_write.c:313 [inline] > SyS_lseek+0xeb/0x170 fs/read_write.c:304 > entry_SYSCALL_64_fastpath+0x23/0x9a > > other info that might help us debug this: > > Chain exists of: > &sb->s_type->i_mutex_key#11 --> &mm->mmap_sem --> ashmem_mutex > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(ashmem_mutex); > lock(&mm->mmap_sem); > lock(ashmem_mutex); > lock(&sb->s_type->i_mutex_key#11); > > *** DEADLOCK *** > > 1 lock held by syzkaller303685/3497: > #0: (ashmem_mutex){+.+.}, at: [<00000000a44304a8>] > ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:334 > > stack backtrace: > CPU: 0 PID: 3497 Comm: syzkaller303685 Not tainted 4.15.0-rc7+ #255 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:17 [inline] > dump_stack+0x194/0x257 lib/dump_stack.c:53 > print_circular_bug.isra.37+0x2cd/0x2dc kernel/locking/lockdep.c:1218 > check_prev_add kernel/locking/lockdep.c:1858 [inline] > check_prevs_add kernel/locking/lockdep.c:1971 [inline] > validate_chain kernel/locking/lockdep.c:2412 [inline] > __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3426 > lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914 > down_write+0x87/0x120 kernel/locking/rwsem.c:70 > inode_lock include/linux/fs.h:713 [inline] > shmem_file_llseek+0xef/0x240 mm/shmem.c:2579 > vfs_llseek+0xa2/0xd0 fs/read_write.c:300 > ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:346 > vfs_llseek fs/read_write.c:300 [inline] > SYSC_lseek fs/read_write.c:313 [inline] > SyS_lseek+0xeb/0x170 fs/read_write.c:304 > entry_SYSCALL_64_fastpath+0x23/0x9a > RIP: 0033:0x444aa9 > RSP: 002b:00007ffd2bec96f8 EFLAGS: 00000217 ORIG_RAX: 0000000000000008 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000444aa9 > RDX: 0000000000000003 RSI: fffffffffffffffc RDI: 0000000000000004 > RBP: 00000000 > > > --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. > If you forgot to add the Reported-by tag, once the fix for this bug is > merged > into any tree, please reply to this email with: > #syz fix: exact-commit-title > If you want to test a patch for this bug, please reply with: > #syz test: git://repo/address.git branch > and provide the patch inline or as an attachment. > To mark this as a duplicate of another syzbot report, please reply with: > #syz dup: exact-subject-of-another-report > If it's a one-off invalid bug report, please reply with: > #syz invalid > Note: if the crash happens again, it will cause creation of a new bug > report. > Note: all commands must start from beginning of the line in the email body. > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit > https://groups.google.com/d/msgid/syzkaller-bugs/001a1144d6e854b3c90562668d74%40google.com. > For more options, visit https://groups.google.com/d/optout. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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