Hello,
syzbot found the following crash on:
HEAD commit: 71fce1ed UPSTREAM: tracing: always define trace_{irq,preem..
git tree: android-4.9
console output:
https://syzkaller.appspot.com/x/log.txt?x=10ddf247800000
kernel config:
https://syzkaller.appspot.com/x/.config?x=a54f56879744de40
dashboard link:
https://syzkaller.appspot.com/bug?extid=9fce278e78218b0d5799
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:
https://syzkaller.appspot.com/x/repro.syz?x=14fa7a47800000
C reproducer:
https://syzkaller.appspot.com/x/repro.c?x=15223a57800000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by:
syzbot+9fce27...@syzkaller.appspotmail.com
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
======================================================
[ INFO: possible circular locking dependency detected ]
4.9.96-g71fce1e #10 Not tainted
-------------------------------------------------------
syz-executor627/3802 is trying to acquire lock:
(&sb->s_type->i_mutex_key#10){++++++}, at: [<ffffffff8149174c>] inode_lock
include/linux/fs.h:766 [inline]
(&sb->s_type->i_mutex_key#10){++++++}, at: [<ffffffff8149174c>]
shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
but task is already holding lock:
(ashmem_mutex){+.+.+.}, at: [<ffffffff82e3ad75>]
ashmem_shrink_scan+0x55/0x3a0 drivers/staging/android/ashmem.c:449
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
__mutex_lock_common kernel/locking/mutex.c:521 [inline]
mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621
ashmem_mmap+0x53/0x3f0 drivers/staging/android/ashmem.c:378
mmap_region+0x893/0x1040 mm/mmap.c:1694
do_mmap+0x4fa/0xc30 mm/mmap.c:1473
do_mmap_pgoff include/linux/mm.h:2032 [inline]
vm_mmap_pgoff+0x168/0x1b0 mm/util.c:329
SYSC_mmap_pgoff mm/mmap.c:1523 [inline]
SyS_mmap_pgoff+0x342/0x550 mm/mmap.c:1481
SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline]
SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87
do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb
lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
__might_fault+0x14a/0x1d0 mm/memory.c:4014
copy_to_user arch/x86/include/asm/uaccess.h:727 [inline]
filldir+0x1a4/0x370 fs/readdir.c:195
dir_emit_dot include/linux/fs.h:3241 [inline]
dir_emit_dots include/linux/fs.h:3252 [inline]
dcache_readdir+0x130/0x5d0 fs/libfs.c:191
iterate_dir+0x1ac/0x600 fs/readdir.c:50
SYSC_getdents fs/readdir.c:230 [inline]
SyS_getdents+0x13c/0x2a0 fs/readdir.c:211
do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb
check_prev_add kernel/locking/lockdep.c:1828 [inline]
check_prevs_add kernel/locking/lockdep.c:1938 [inline]
validate_chain kernel/locking/lockdep.c:2265 [inline]
__lock_acquire+0x3019/0x4070 kernel/locking/lockdep.c:3345
lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
down_write+0x41/0xa0 kernel/locking/rwsem.c:52
inode_lock include/linux/fs.h:766 [inline]
shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
ashmem_shrink_scan+0x1bd/0x3a0 drivers/staging/android/ashmem.c:456
ashmem_ioctl+0x2c1/0xf20 drivers/staging/android/ashmem.c:798
vfs_ioctl fs/ioctl.c:43 [inline]
file_ioctl fs/ioctl.c:493 [inline]
do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
SYSC_ioctl fs/ioctl.c:694 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
entry_SYSCALL_64_after_swapgs+0x5d/0xdb
other info that might help us debug this:
Chain exists of:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(ashmem_mutex);
lock(&mm->mmap_sem);
lock(ashmem_mutex);
lock(&sb->s_type->i_mutex_key#10);
*** DEADLOCK ***
1 lock held by syz-executor627/3802:
#0: (ashmem_mutex){+.+.+.}, at: [<ffffffff82e3ad75>]
ashmem_shrink_scan+0x55/0x3a0 drivers/staging/android/ashmem.c:449
stack backtrace:
CPU: 1 PID: 3802 Comm: syz-executor627 Not tainted 4.9.96-g71fce1e #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d94ff638 ffffffff81eb0b69 ffffffff853d0a10 ffffffff853eee60
ffffffff853d8030 ffff8801b7fe88e8 ffff8801b7fe8000 ffff8801d94ff680
ffffffff814242fd 0000000000000001 00000000b7fe8000 0000000000000001
Call Trace:
[<ffffffff81eb0b69>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81eb0b69>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff814242fd>] print_circular_bug.cold.51+0x1bd/0x27d
kernel/locking/lockdep.c:1202
[<ffffffff81237399>] check_prev_add kernel/locking/lockdep.c:1828 [inline]
[<ffffffff81237399>] check_prevs_add kernel/locking/lockdep.c:1938 [inline]
[<ffffffff81237399>] validate_chain kernel/locking/lockdep.c:2265 [inline]
[<ffffffff81237399>] __lock_acquire+0x3019/0x4070
kernel/locking/lockdep.c:3345
[<ffffffff81238e60>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
[<ffffffff839ece01>] down_write+0x41/0xa0 kernel/locking/rwsem.c:52
[<ffffffff8149174c>] inode_lock include/linux/fs.h:766 [inline]
[<ffffffff8149174c>] shmem_fallocate+0x13c/0xb40 mm/shmem.c:2674
[<ffffffff82e3aedd>] ashmem_shrink_scan+0x1bd/0x3a0
drivers/staging/android/ashmem.c:456
[<ffffffff82e3b5b1>] ashmem_ioctl+0x2c1/0xf20
drivers/staging/android/ashmem.c:798
[<ffffffff815b051c>] vfs_ioctl fs/ioctl.c:43 [inline]
[<ffffffff815b051c>] file_ioctl fs/ioctl.c:493 [inline]
[<ffffffff815b051c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
[<ffffffff815b159f>] SYSC_ioctl fs/ioctl.c:694 [inline]
[<ffffffff815b159f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
[<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
[<ffffffff839f3313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
random: crng init done