On 2017/11/21 16:35, syzbot wrote:
> Hello,
>
> syzkaller hit the following crash on ca91659962303d4fd5211a5e4e13df5cbb11e744
> 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.
>
> Unfortunately, I don't have any reproducer for this bug yet.
Fault injection found an unchecked register_shrinker() return code.
Wow, register_shrinker()/unregister_shinker() is possibly frequently called path?
struct super_block *sget_userns(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
int flags, struct user_namespace *user_ns,
void *data)
{
(...snipped...)
spin_unlock(&sb_lock);
get_filesystem(type);
register_shrinker(&s->s_shrink); // Error check required.
return s;
}
[ 554.881422] FAULT_INJECTION: forcing a failure.
[ 554.881422] name failslab, interval 1, probability 0, space 0, times 0
[ 554.881438] CPU: 1 PID: 13231 Comm: syz-executor1 Not tainted 4.14.0-rc8+ #82
[ 554.881443] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[ 554.881445] Call Trace:
[ 554.881459] dump_stack+0x194/0x257
[ 554.881474] ? arch_local_irq_restore+0x53/0x53
[ 554.881486] ? find_held_lock+0x35/0x1d0
[ 554.881507] should_fail+0x8c0/0xa40
[ 554.881522] ? fault_create_debugfs_attr+0x1f0/0x1f0
[ 554.881537] ? check_noncircular+0x20/0x20
[ 554.881546] ? find_next_zero_bit+0x2c/0x40
[ 554.881560] ? ida_get_new_above+0x421/0x9d0
[ 554.881577] ? find_held_lock+0x35/0x1d0
[ 554.881594] ? __lock_is_held+0xb6/0x140
[ 554.881628] ? check_same_owner+0x320/0x320
[ 554.881634] ? lock_downgrade+0x990/0x990
[ 554.881649] ? find_held_lock+0x35/0x1d0
[ 554.881672] should_failslab+0xec/0x120
[ 554.881684] __kmalloc+0x63/0x760
[ 554.881692] ? lock_downgrade+0x990/0x990
[ 554.881712] ? register_shrinker+0x10e/0x2d0
[ 554.881721] ? trace_event_raw_event_module_request+0x320/0x320
[ 554.881737] register_shrinker+0x10e/0x2d0
[ 554.881747] ? prepare_kswapd_sleep+0x1f0/0x1f0
[ 554.881755] ? _down_write_nest_lock+0x120/0x120
[ 554.881765] ? memcpy+0x45/0x50
[ 554.881785] sget_userns+0xbcd/0xe20
[ 554.881792] ? set_anon_super+0x20/0x20
[ 554.881809] ? put_filp+0x90/0x90
[ 554.881822] ? __sb_start_write+0x2a0/0x2a0
[ 554.881829] ? alloc_pages_current+0xbe/0x1e0
[ 554.881846] ? free_pages+0x51/0x90
[ 554.881858] ? selinux_sb_copy_data+0x4a1/0x610
[ 554.881864] ? __lockdep_init_map+0xe4/0x650
[ 554.881882] ? selinux_quota_on+0x320/0x320
[ 554.881892] ? __lockdep_init_map+0xe4/0x650
[ 554.881906] ? lockdep_init_map+0x9/0x10
[ 554.881936] ? mqueue_get_inode+0xc60/0xc60
[ 554.881944] mount_ns+0x6d/0x190
[ 554.881960] mqueue_mount+0xbe/0xe0
[ 554.881975] mount_fs+0x66/0x2d0
[ 554.881991] vfs_kern_mount.part.26+0xc6/0x4a0
[ 554.882004] ? may_umount+0xa0/0xa0
[ 554.882013] ? compat_SyS_msgrcv+0x50/0x50
[ 554.882023] ? ida_remove+0x3e0/0x3e0
[ 554.882034] ? kmem_cache_alloc_trace+0x456/0x750
[ 554.882048] kern_mount_data+0x50/0xb0
[ 554.898693] kasan: CONFIG_KASAN_INLINE enabled
[ 554.898724] kasan: GPF could be caused by NULL-ptr deref or user memory access
[ 554.898732] general protection fault: 0000 [#1] SMP KASAN
[ 554.898737] Dumping ftrace buffer:
[ 554.898741] (ftrace buffer empty)
[ 554.898743] Modules linked in:
[ 554.898752] CPU: 1 PID: 13231 Comm: syz-executor1 Not tainted 4.14.0-rc8+ #82
[ 554.898755] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[ 554.898760] task: ffff8801d1dbe5c0 task.stack: ffff8801c9e38000
[ 554.898772] RIP: 0010:__list_del_entry_valid+0x7e/0x150
[ 554.898775] RSP: 0018:ffff8801c9e3f108 EFLAGS: 00010246
[ 554.898780] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 554.898784] RDX: 0000000000000000 RSI: ffff8801c53c6f98 RDI: ffff8801c53c6fa0
[ 554.898788] RBP: ffff8801c9e3f120 R08: 1ffff100393c7d55 R09: 0000000000000004
[ 554.898791] R10: ffff8801c9e3ef70 R11: 0000000000000000 R12: 0000000000000000
[ 554.898795] R13: dffffc0000000000 R14: 1ffff100393c7e45 R15: ffff8801c53c6f98
[ 554.898800] FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
[ 554.898804] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
[ 554.898807] CR2: 00000000dbc23000 CR3: 00000001c7269000 CR4: 00000000001406e0
[ 554.898813] DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
[ 554.898816] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
[ 554.898818] Call Trace:
[ 554.898828] unregister_shrinker+0x79/0x300
[ 554.898837] ? perf_trace_mm_vmscan_writepage+0x750/0x750
[ 554.898844] ? down_write+0x87/0x120
[ 554.898851] ? deactivate_super+0x139/0x1b0
[ 554.898857] ? down_read+0x150/0x150
[ 554.898864] ? check_same_owner+0x320/0x320
[ 554.898875] deactivate_locked_super+0x64/0xd0
[ 554.898883] deactivate_super+0x141/0x1b0
[ 554.898893] ? mount_ns+0x190/0x190
[ 554.898901] ? dput.part.24+0x175/0x740
[ 554.898912] cleanup_mnt+0xb2/0x150
[ 554.898919] mntput_no_expire+0x6e0/0xa90
[ 554.898926] ? call_rcu_bh+0x20/0x20
[ 554.898934] ? mnt_get_count+0x150/0x150
[ 554.898942] ? trace_raw_output_rcu_utilization+0xb0/0xb0
[ 554.898954] ? __might_sleep+0x95/0x190
[ 554.898964] kern_unmount+0x9c/0xd0
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