random: sshd: uninitialized urandom read (32 bytes read, 123 bits of entropy available)
======================================================
[ INFO: possible circular locking dependency detected ]
4.4.113-ge70c132 #27 Not tainted
-------------------------------------------------------
syzkaller885830/3313 is trying to acquire lock:
(&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff81462321>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
but task is already holding lock:
(ashmem_mutex){+.+.+.}, at: [<ffffffff82c60746>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
[<ffffffff8123c77e>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
[<ffffffff8376858b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
[<ffffffff8376858b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
[<ffffffff82c5fb93>] ashmem_mmap+0x53/0x400 drivers/staging/android/ashmem.c:366
[<ffffffff814afd6f>] mmap_region+0x94f/0x1250 mm/mmap.c:1664
[<ffffffff814b0b6d>] do_mmap+0x4fd/0x9d0 mm/mmap.c:1441
[<ffffffff8146efee>] do_mmap_pgoff include/linux/mm.h:1915 [inline]
[<ffffffff8146efee>] vm_mmap_pgoff+0x16e/0x1c0 mm/util.c:272
[<ffffffff814aed3f>] SYSC_mmap_pgoff mm/mmap.c:1491 [inline]
[<ffffffff814aed3f>] SyS_mmap_pgoff+0x33f/0x560 mm/mmap.c:1449
[<ffffffff81006d74>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
[<ffffffff81006d74>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
[<ffffffff837734ea>] sysenter_flags_fixed+0xd/0x17
[<ffffffff8123c77e>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
[<ffffffff8149460a>] __might_fault+0x14a/0x1d0 mm/memory.c:3810
[<ffffffff81559642>] copy_to_user arch/x86/include/asm/uaccess.h:760 [inline]
[<ffffffff81559642>] filldir+0x162/0x2d0 fs/readdir.c:180
[<ffffffff81596c7e>] dir_emit_dot include/linux/fs.h:3070 [inline]
[<ffffffff81596c7e>] dir_emit_dots include/linux/fs.h:3081 [inline]
[<ffffffff81596c7e>] dcache_readdir+0x11e/0x7b0 fs/libfs.c:150
[<ffffffff81559288>] iterate_dir+0x1c8/0x420 fs/readdir.c:42
[<ffffffff81559f7a>] SYSC_getdents fs/readdir.c:215 [inline]
[<ffffffff81559f7a>] SyS_getdents+0x14a/0x270 fs/readdir.c:196
[<ffffffff83771b5f>] entry_SYSCALL_64_fastpath+0x1c/0x98
[<ffffffff81239adf>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
[<ffffffff81239adf>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
[<ffffffff81239adf>] validate_chain kernel/locking/lockdep.c:2144 [inline]
[<ffffffff81239adf>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
[<ffffffff8123c77e>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
[<ffffffff8376858b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
[<ffffffff8376858b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
[<ffffffff81462321>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
[<ffffffff8151b4c2>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
[<ffffffff82c607d7>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
[<ffffffff8151d43b>] vfs_llseek fs/read_write.c:260 [inline]
[<ffffffff8151d43b>] SYSC_lseek fs/read_write.c:285 [inline]
[<ffffffff8151d43b>] SyS_lseek fs/read_write.c:276 [inline]
[<ffffffff8151d43b>] C_SYSC_lseek fs/read_write.c:297 [inline]
[<ffffffff8151d43b>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
[<ffffffff81006d74>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
[<ffffffff81006d74>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
[<ffffffff837734ea>] sysenter_flags_fixed+0xd/0x17
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 syzkaller885830/3313:
#0: (ashmem_mutex){+.+.+.}, at: [<ffffffff82c60746>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330
stack backtrace:
CPU: 0 PID: 3313 Comm: syzkaller885830 Not tainted 4.4.113-ge70c132 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
0000000000000000 f567d1bab61a0a9c ffff8801d1b6fa58 ffffffff81d0278d
ffffffff851a0560 ffffffff851aa250 ffffffff851beb60 ffff8800b5168898
ffff8800b5168000 ffff8801d1b6faa0 ffffffff81232b51 ffff8800b5168898
Call Trace:
[<ffffffff81d0278d>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81d0278d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
[<ffffffff81232b51>] print_circular_bug+0x271/0x310 kernel/locking/lockdep.c:1226
[<ffffffff81239adf>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
[<ffffffff81239adf>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
[<ffffffff81239adf>] validate_chain kernel/locking/lockdep.c:2144 [inline]
[<ffffffff81239adf>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
[<ffffffff8123c77e>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
[<ffffffff8376858b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
[<ffffffff8376858b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
[<ffffffff81462321>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
[<ffffffff8151b4c2>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
[<ffffffff82c607d7>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
[<ffffffff8151d43b>] vfs_llseek fs/read_write.c:260 [inline]
[<ffffffff8151d43b>] SYSC_lseek fs/read_write.c:285 [inline]
[<ffffffff8151d43b>] SyS_lseek fs/read_write.c:276 [inline]
[<ffffffff8151d43b>] C_SYSC_lseek fs/read_write.c:297 [inline]
[<ffffffff8151d43b>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
[<ffffffff81006d74>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
[<ffffffff81006d74>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
[<ffffffff837734ea>] sysent