Re: possible deadlock in __do_page_fault

From: syzbot
Date: Mon Oct 01 2018 - 01:23:28 EST

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syzbot has found a reproducer for the following crash on:

HEAD commit: 17b57b1883c1 Linux 4.19-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17920a7e400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0af03fe452b65fb
dashboard link: https://syzkaller.appspot.com/bug?extid=a76129f18c89f3e2ddd4
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=160c0f11400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1788de81400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a76129f18c89f3e2ddd4@xxxxxxxxxxxxxxxxxxxxxxxxx

audit: type=1800 audit(1538371187.479:30): pid=5202 uid=0 auid=4294967295 ses=4294967295 subj=_ op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0

======================================================
WARNING: possible circular locking dependency detected
4.19.0-rc6+ #39 Not tainted
------------------------------------------------------
syz-executor559/5371 is trying to acquire lock:
00000000e34677d1 (&mm->mmap_sem){++++}, at: __do_page_fault+0xb70/0xed0 arch/x86/mm/fault.c:1331

but task is already holding lock:
00000000b0c242ca (&sb->s_type->i_mutex_key#11){+.+.}, at: inode_lock include/linux/fs.h:738 [inline]
00000000b0c242ca (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xed/0x870 mm/filemap.c:3289

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#11){+.+.}:
down_write+0x8a/0x130 kernel/locking/rwsem.c:70
inode_lock include/linux/fs.h:738 [inline]
shmem_fallocate+0x18b/0x12c0 mm/shmem.c:2651
ashmem_shrink_scan+0x238/0x660 drivers/staging/android/ashmem.c:455
ashmem_ioctl+0x3ae/0x13a0 drivers/staging/android/ashmem.c:797
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (ashmem_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:925 [inline]
__mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
ashmem_mmap+0x55/0x520 drivers/staging/android/ashmem.c:361
call_mmap include/linux/fs.h:1813 [inline]
mmap_region+0xe82/0x1cd0 mm/mmap.c:1762
do_mmap+0xa10/0x1220 mm/mmap.c:1535
do_mmap_pgoff include/linux/mm.h:2298 [inline]
vm_mmap_pgoff+0x213/0x2c0 mm/util.c:357
ksys_mmap_pgoff+0x4da/0x660 mm/mmap.c:1585
__do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
__se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
__x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&mm->mmap_sem){++++}:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900
down_read+0xb0/0x1d0 kernel/locking/rwsem.c:24
__do_page_fault+0xb70/0xed0 arch/x86/mm/fault.c:1331
do_page_fault+0xf2/0x7e0 arch/x86/mm/fault.c:1470
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1161
fault_in_pages_readable include/linux/pagemap.h:609 [inline]
iov_iter_fault_in_readable+0x363/0x450 lib/iov_iter.c:421
generic_perform_write+0x216/0x6a0 mm/filemap.c:3129
__generic_file_write_iter+0x26e/0x630 mm/filemap.c:3264
generic_file_write_iter+0x436/0x870 mm/filemap.c:3292
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#11

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#11);
lock(ashmem_mutex);
lock(&sb->s_type->i_mutex_key#11);
lock(&mm->mmap_sem);

*** DEADLOCK ***

2 locks held by syz-executor559/5371:
#0: 0000000012b388bb (sb_writers#5){.+.+}, at: file_start_write include/linux/fs.h:2759 [inline]
#0: 0000000012b388bb (sb_writers#5){.+.+}, at: vfs_write+0x42a/0x560 fs/read_write.c:548
#1: 00000000b0c242ca (&sb->s_type->i_mutex_key#11){+.+.}, at: inode_lock include/linux/fs.h:738 [inline]
#1: 00000000b0c242ca (&sb->s_type->i_mutex_key#11){+.+.}, at: generic_file_write_iter+0xed/0x870 mm/filemap.c:3289

stack backtrace:
CPU: 1 PID: 5371 Comm: syz-executor559 Not tainted 4.19.0-rc6+ #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
print_circular_bug.isra.33.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1221
check_prev_add kernel/locking/lockdep.c:1861 [inline]
check_prevs_add kernel/locking/lockdep.c:1974 [inline]
validate_chain kernel/locking/lockdep.c:2415 [inline]
__lock_acquire+0x33e4/0x4ec0 kernel/locking/lockdep.c:3411
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900
down_read+0xb0/0x1d0 kernel/locking/rwsem.c:24
__do_page_fault+0xb70/0xed0 arch/x86/mm/fault.c:1331
do_page_fault+0xf2/0x7e0 arch/x86/mm/fault.c:1470
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1161
RIP: 0010:fault_in_pages_readable include/linux/pagemap.h:609 [inline]
RIP: 0010:iov_iter_fault_in_readable+0x363/0x450 lib/iov_iter.c:421
Code: 00 31 ff 44 89 ee 88 55 98 e8 59 27 f4 fd 45 85 ed 74 c2 e9 7d fe ff ff e8 3a 26 f4 fd 0f 1f 00 0f ae e8 48 8b 85 28 ff ff ff <8a> 00 0f 1f 00 31 ff 89 de 88 85 58 ff ff ff e8 29 27 f4 fd 85 db
RSP: 0018:ffff8801bf4e77d0 EFLAGS: 00010293
RAX: 000000002100053f RBX: 0000000000000000 RCX: ffffffff838a8de2
RDX: 0000000000000000 RSI: ffffffff838a8f46 RDI: 0000000000000007
RBP: ffff8801bf4e78a8 R08: ffff8801d81b24c0 R09: fffff94000da818e
R10: fffff94000da818e R11: ffffea0006d40c77 R12: 0000000000000000
R13: 0000000000001000 R14: 0000000000001000 R15: ffff8801bf4e7bc8
generic_perform_write+0x216/0x6a0 mm/filemap.c:3129
__generic_file_write_iter+0x26e/0x630 mm/filemap.c:3264
generic_file_write_iter+0x436/0x870 mm/filemap.c:3292
call_write_iter include/linux/fs.h:1808 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x6b8/0x9f0 fs/read_write.c:487
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x446339
Code: e8 2c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff3053d5da8 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dac28 RCX: 0000000000446339
RDX: 00000000fffffda2 RSI: 0000000020000540 RDI: 0000000000000003
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00000000006dac2c
R13: dfdd4f11168a8b2b R14: 6873612f7665642f R15: 00000000006dad2c
kobject: 'regulatory.0' (000000004f5af2e3): kobject_uevent_env
kobject: 'regulatory.0' (000000004f5af2e3): fill_kobj_path: path = '/devices/platform/regulatory.0'

Next message: Brian Masney: "[PATCH RFC 5/5] ARM: dts: qcom: msm8974-hammerhead: add USB OTG support"
Previous message: Viresh Kumar: "Re: [PATCH] PM / OPP: Refactor counting of added OPPs for v2 to avoid unsupported OPPs"
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