On Sat, Mar 21, 2020 at 12:15 AM Dmitry Vyukov [off-list ref] wrote:

On Sat, Mar 21, 2020 at 8:12 AM syzbot
[off-list ref] wrote:

quoted

Hello,

syzbot found the following crash on:

HEAD commit:    fb33c651 Linux 5.6-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=140688d3e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9f894bd92023de02
dashboard link: https://syzkaller.appspot.com/bug?extid=c07afbbb410e9f712273
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c07afbbb410e9f712273@syzkaller.appspotmail.com

+ashmem maintainers

We'll have a look.

From the log, ashmem spews an infinite sequence of some errors which
probably stall the machine:

[ 1094.685541][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641097791
[ 1094.701750][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641383141
[ 1094.708003][ T9576] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641233534
[ 1094.723597][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641083174
[ 1094.730025][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641098111
[ 1094.745592][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641383221
[ 1094.753153][ T9576] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641233534
[ 1094.767903][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641084454
[ 1094.819845][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641526579
[ 1094.830116][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641098111
[ 1094.845813][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641527219
[ 1094.852188][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641098751
[ 1094.871456][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641527219
[ 1094.874256][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641098751
[ 1094.890195][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641528499
[ 1094.895999][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641087014
[ 1094.912931][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641528499
[ 1094.918797][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641100031
[ 1094.936636][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641531059
[ 1094.941391][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641081897
[ 1094.957463][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641531059
[ 1094.963568][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641100031
[ 1094.980233][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641536179
[ 1094.985311][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641081899
[ 1095.001393][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641536179
[ 1095.008146][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641102591
[ 1095.024425][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525942
[ 1095.029644][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641081904
[ 1095.046399][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525942
[ 1095.052377][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641102591
[ 1095.068000][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525944
[ 1095.073934][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641081914
[ 1095.091076][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525944
[ 1095.096925][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641107711
[ 1095.112305][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525949
[ 1095.118570][ T1876] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641081934
[ 1095.135413][ T7239] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641525949
[ 1095.141206][ T9460] vmscan: shrink_slab:
ashmem_shrink_scan+0x0/0x500 negative objects to delete
nr=-6917529027641107711

quoted

INFO: task syz-executor.4:7237 blocked for more than 143 seconds.
      Not tainted 5.6.0-rc6-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D26576  7237   9609 0x00004004
Call Trace:
 schedule+0xd0/0x2a0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 blk_trace_remove+0x1e/0x40 kernel/trace/blktrace.c:361
 sg_ioctl_common+0x221/0x2710 drivers/scsi/sg.c:1125
 sg_ioctl+0x8f/0x120 drivers/scsi/sg.c:1159
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: Bad RIP value.
RSP: 002b:00007f5ba5a3bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5ba5a3c6d4 RCX: 000000000045c849
RDX: 0000000000000000 RSI: 0000000000001276 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000022b R14: 00000000004c4526 R15: 000000000076bf0c
INFO: task syz-executor.4:7266 blocked for more than 146 seconds.
      Not tainted 5.6.0-rc6-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D27752  7266   9609 0x00004004
Call Trace:
 schedule+0xd0/0x2a0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 blk_trace_setup+0x2f/0x60 kernel/trace/blktrace.c:588
 sg_ioctl_common+0x2f2/0x2710 drivers/scsi/sg.c:1116
 sg_ioctl+0x8f/0x120 drivers/scsi/sg.c:1159
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: Bad RIP value.
RSP: 002b:00007f5ba5a1ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5ba5a1b6d4 RCX: 000000000045c849
RDX: 0000000020000080 RSI: 00000000c0481273 RDI: 0000000000000008
RBP: 000000000076bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000228 R14: 00000000004c44eb R15: 000000000076bfac
INFO: task syz-executor.5:7265 blocked for more than 149 seconds.
      Not tainted 5.6.0-rc6-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D26736  7265   9613 0x00004004
Call Trace:
 schedule+0xd0/0x2a0 kernel/sched/core.c:4154
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4213
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
 blk_trace_setup+0x2f/0x60 kernel/trace/blktrace.c:588
 sg_ioctl_common+0x2f2/0x2710 drivers/scsi/sg.c:1116
 sg_ioctl+0x8f/0x120 drivers/scsi/sg.c:1159
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:770
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: Bad RIP value.
RSP: 002b:00007f576f48ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f576f48b6d4 RCX: 000000000045c849
RDX: 0000000020000080 RSI: 00000000c0481273 RDI: 0000000000000006


---
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