uvm_fault: VOP_LOCK (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 25b30cac31a3 sort
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=12cd40fd180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7058272de1526588
dashboard link: https://syzkaller.appspot.com/bug?extid=5eb5e269f7c81c767acc

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a2564b1f7252/disk-25b30cac.raw.xz
bsd.gdb: https://storage.googleapis.com/syzbot-assets/319d6a006bad/bsd-25b30cac.gdb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1162abc82f00/kernel-25b30cac.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5eb5e2...@syzkaller.appspotmail.com

uvm_fault(0xffffffff82d6c698, 0x0, 0, 1) -> e
kernel: page fault trap, code=0
Stopped at VOP_LOCK+0x72: movq 0(%rax),%r14
TID PID UID PRFLAGS PFLAGS CPU COMMAND
334782 25253 0 0x14000 0x200 0 zerothread
*195350 61180 0 0x14000 0x200 1 update
VOP_LOCK(fffffd807d4db6f8,41) at VOP_LOCK+0x72 sys/kern/vfs_vops.c:515
vn_lock(fffffd807d4db6f8,41) at vn_lock+0x85 sys/kern/vfs_vnops.c:564
vget(fffffd807d4db6f8,41) at vget+0x1fd sys/kern/vfs_subr.c:676
syncer_thread(ffff80002a148a48) at syncer_thread+0xbd sys/kern/vfs_sync.c:150
end trace frame: 0x0, count: 11
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports. Insufficient info makes it difficult to find and fix bugs.
ddb{1}>
ddb{1}> set $lines = 0
ddb{1}> set $maxwidth = 0
ddb{1}> show panic
*cpu1: uvm_fault(0xffffffff82d6c698, 0x0, 0, 1) -> e
ddb{1}> trace
VOP_LOCK(fffffd807d4db6f8,41) at VOP_LOCK+0x72 sys/kern/vfs_vops.c:515
vn_lock(fffffd807d4db6f8,41) at vn_lock+0x85 sys/kern/vfs_vnops.c:564
vget(fffffd807d4db6f8,41) at vget+0x1fd sys/kern/vfs_subr.c:676
syncer_thread(ffff80002a148a48) at syncer_thread+0xbd sys/kern/vfs_sync.c:150
end trace frame: 0x0, count: -4
ddb{1}> show registers
rdi 0
rsi 0
rbp 0xffff80002a167590
rbx 0xffff800029cebff0
rdx 0
rcx 0xffff80002a148a48
rax 0
r8 0xffffffffffffffff
r9 0x1
r10 0x47e6641091500b83
r11 0xc4279a9016c1a986
r12 0
r13 0
r14 0xfffffd807d4db6f8
r15 0
rip 0xffffffff82237592 VOP_LOCK+0x72
cs 0x8
rflags 0x10203 __ALIGN_SIZE+0xf203
rsp 0xffff80002a167540
ss 0x10
VOP_LOCK+0x72: movq 0(%rax),%r14
ddb{1}> show proc
PROC (update) tid=195350 pid=61180 tcnt=1 stat=onproc
flags process=14000<NOZOMBIE,SYSTEM> proc=200<SYSTEM>
runpri=40, usrpri=51, slppri=40, nice=20
wchan=0x0, wmesg=, ps_single=0x0
forw=0xffffffffffffffff, list=0xffff80002a148f68,0xffff80002a1487c8
process=0xffff80002a15a7f8 user=0xffff80002a162000, vmspace=0xffffffff82d6c698
estcpu=1, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{1}> ps
PID TID PPID UID S FLAGS WAIT COMMAND
60152 510529 10079 0 3 0x810008a sigsusp sh
10079 201494 80124 0 3 0x8000082 wait syz-executor.2
13065 196881 80124 0 2 0x8000002 syz-executor.1
43963 332081 80124 0 3 0x8000082 wait syz-executor.7
30377 375184 80124 0 3 0x8000082 wait syz-executor.0
51096 478471 80124 0 3 0x8000082 wait syz-executor.5
25636 136281 80124 0 3 0x8000082 wait syz-executor.4
85442 108931 80124 0 3 0x8000082 wait syz-executor.3
67816 519436 80124 0 3 0x8000082 wait syz-executor.6
37580 100587 0 0 3 0x14200 acct acct
2205 498772 0 0 3 0x14200 bored sosplice
80124 353477 37679 0 3 0x1a000082 wait syz-fuzzer
80124 265392 37679 0 3 0x1e000082 nanoslp syz-fuzzer
80124 344982 37679 0 3 0x1e000082 wait syz-fuzzer
80124 463191 37679 0 3 0x1e000082 wait syz-fuzzer
80124 116822 37679 0 3 0x1e000082 wait syz-fuzzer
80124 108813 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 265387 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 382821 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 99572 37679 0 3 0x1e000082 wait syz-fuzzer
80124 375819 37679 0 3 0x1e000082 wait syz-fuzzer
80124 503675 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 181815 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 375720 37679 0 3 0x1e000082 wait syz-fuzzer
80124 63306 37679 0 3 0x1e000082 thrsleep syz-fuzzer
80124 143751 37679 0 2 0x1e000482 syz-fuzzer
80124 468135 37679 0 3 0x1e000082 wait syz-fuzzer
37679 427485 69515 0 3 0x810008a sigsusp ksh
69515 156367 58316 0 3 0x1800009a kqread sshd
43654 274596 1 0 3 0x18100083 ttyin getty
58316 161648 1 0 3 0x18000088 kqread sshd
25044 425906 85583 74 3 0x19100092 bpf pflogd
85583 286089 1 0 3 0x18000080 sbwait pflogd
79601 357454 42492 73 2 0x19100010 syslogd
42492 436294 1 0 3 0x18100082 sbwait syslogd
61585 166549 1 0 3 0x18100080 kqread resolvd
22571 340148 46192 77 3 0x18100092 kqread dhcpleased
97653 107441 46192 77 3 0x18100092 kqread dhcpleased
46192 293835 1 0 3 0x18000080 kqread dhcpleased
46772 358121 0 0 3 0x14200 bored smr
25253 334782 0 0 7 0x14200 zerothread
26933 257289 0 0 3 0x14200 aiodoned aiodoned
*61180 195350 0 0 7 0x14200 update
242 22611 0 0 3 0x14200 cleaner cleaner
83984 240200 0 0 2 0x14200 reaper
79597 188246 0 0 3 0x14200 pgdaemon pagedaemon
27347 297704 0 0 3 0x14200 bored viomb
20172 172907 0 0 3 0x40014200 acpi0 acpi0
17648 346684 0 0 3 0x40014200 idle1
15049 452820 0 0 3 0x14200 bored softnet3
57530 172991 0 0 3 0x14200 bored softnet2
61291 384753 0 0 3 0x14200 bored softnet1
3540 8321 0 0 3 0x14200 bored softnet0
65789 338873 0 0 2 0x14200 systqmp
31096 445462 0 0 3 0x14200 bored systq
83679 182404 0 0 3 0x14200 tmoslp softclockmp
3280 264203 0 0 3 0x40014200 tmoslp softclock
83766 440292 0 0 3 0x40014200 idle0
1 91249 0 0 3 0x8000082 wait init
0 0 -1 0 3 0x10200 scheduler swapper
ddb{1}> show all locks
CPU 0:
exclusive mutex &uvm.fpageqlock r = 0 (0xffffffff82e98fa8)
#0 witness_lock+0x446 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x446 sys/kern/subr_witness.c:1187
#1 mtx_enter_try+0x103
#2 mtx_enter+0x4e sys/kern/kern_lock.c:266
#3 uvm_pagezero_thread+0x1a1 sys/uvm/uvm_pmemrange.c:2185
#4 proc_trampoline+0x10
Process 13065 (syz-executor.1) thread 0xffff80002a1c07d0 (196881)
Process 79601 (syslogd) thread 0xffff8000ffffd720 (357454)
Process 61180 (update) thread 0xffff80002a148a48 (195350)
Process 83984 (reaper) thread 0xffff80002a1491f8 (240200)
ddb{1}> show malloc
Type InUse MemUse HighUse Limit Requests Type Lim
devbuf 10189 6493K 6611K 166960K 11557 0
pcb 17 12K 12K 166960K 150 0
rtable 239 7K 8K 166960K 985 0
pf 32 9K 10K 166960K 110 0
ifaddr 45 15K 16K 166960K 133 0
ifgroup 55 2K 2K 166960K 174 0
sysctl 3 0K 0K 166960K 3 0
counters 64 36K 36K 166960K 122 0
ioctlops 0 0K 4K 166960K 1565 0
iov 0 0K 16K 166960K 86 0
mount 1 1K 1K 166960K 1 0
log 0 0K 0K 166960K 4 0
vnodes 1368 86K 86K 166960K 2002 0
UFS quota 1 32K 32K 166960K 1 0
UFS mount 5 36K 36K 166960K 5 0
shm 2 1K 9K 166960K 41 0
VM map 2 1K 1K 166960K 2 0
sem 12 0K 0K 166960K 66 0
dirhash 12 2K 3K 166960K 42 0
ACPI 1697 195K 286K 166960K 12548 0
file desc 11 37K 85K 166960K 1324 0
sigio 0 0K 0K 166960K 37 0
proc 70 91K 128K 166960K 1059 0
subproc 104 6K 6K 166960K 312 0
NFS srvsock 1 0K 0K 166960K 1 0
NFS daemon 1 16K 16K 166960K 1 0
ip_moptions 0 0K 0K 166960K 152 0
in_multi 89 6K 7K 166960K 315 0
ether_multi 1 0K 0K 166960K 5 0
mrt 2 0K 0K 166960K 7 0
ISOFS mount 1 32K 32K 166960K 1 0
MSDOSFS mount 1 16K 16K 166960K 1 0
ttys 85 387K 387K 166960K 85 0
exec 0 0K 1K 166960K 697 0
pfkey data 0 0K 0K 166960K 4 0
tdb 3 0K 0K 166960K 3 0
VM swap 8 62K 64K 166960K 10 0
UVM amap 361 141K 143K 166960K 13561 0
UVM aobj 47 2K 2K 166960K 56 0
pinsyscall 35 70K 108K 166960K 2918 0
memdesc 1 4K 4K 166960K 1 0
crypto data 1 1K 1K 166960K 1 0
ip6_options 0 0K 1K 166960K 89 0
NDP 12 0K 2K 166960K 87 0
temp 76 6816K 6888K 166960K 29698 0
kqueue 12 18K 26K 166960K 162 0
SYN cache 2 16K 16K 166960K 2 0
ddb{1}> show all pools
Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
plcache 128 24 0 0 1 0 1 1 0 8 0
rtpcb 120 142 0 139 1 0 1 1 0 8 0
rtentry 112 342 0 233 4 0 4 4 0 8 0
unpcb 144 1007 0 992 7 6 1 4 0 8 0
syncache 336 4 0 4 1 1 0 1 0 8 0
tcpqe 32 18 0 18 1 1 0 1 0 8 0
tcpcb 808 272 0 267 4 3 1 2 0 8 0
arp 120 71 0 51 1 0 1 1 0 8 0
inpcb 392 1137 0 1129 8 6 2 3 0 8 1
nd6 136 77 0 54 1 0 1 1 0 8 0
pkpcb 40 8 0 8 6 6 0 1 0 8 0
kcovpl 48 24 0 16 1 0 1 1 0 8 0
ppxss 1168 5 0 5 5 5 0 1 0 8 0
pffrag 232 9 0 4 1 0 1 1 0 482 0
pffrnode 88 9 0 4 1 0 1 1 0 8 0
pffrent 40 12 0 7 1 0 1 1 0 8 0
pfosfp 40 1428 0 1005 5 0 5 5 0 8 0
pfosfpen 112 1428 0 714 21 0 21 21 0 8 0
pfstitem 24 93 0 67 1 0 1 1 0 8 0
pfstkey 128 93 0 67 2 0 2 2 0 8 0
pfstate 376 93 0 67 5 1 4 4 0 8 0
pfrule 1344 21 0 16 2 1 1 2 0 8 0
art_heap8 4096 1 0 0 1 0 1 1 0 8 0
art_heap4 256 1215 0 792 37 8 29 30 0 8 0
art_table 32 1216 0 792 4 0 4 4 0 8 0
art_node 16 336 0 242 1 0 1 1 0 8 0
sysvmsgpl 40 19 0 12 1 0 1 1 0 8 0
semupl 112 2 0 2 2 2 0 1 0 8 0
semapl 112 64 0 54 1 0 1 1 0 8 0
shmpl 112 53 0 9 2 0 2 2 0 8 0
dirhash 1024 37 0 20 3 0 3 3 0 8 0
dino2pl 256 3376 0 1847 97 0 97 97 0 8 0
ffsino 272 3376 0 1847 103 0 103 103 0 8 0
nchpl 144 5243 0 3500 67 0 67 67 0 8 0
uvmvnodes 80 3801 0 0 78 0 78 78 0 8 0
vnodes 216 3801 0 0 212 0 212 212 0 8 0
vnodes: pool(0xffffffff82d6d0f8:vnodes): page inconsistency: page 0x0; at page head addr 0xfffffd807d4dbf90 (p 0xfffffd807d4db000)
namei 1024 18191 0 18190 3 2 1 2 0 8 0
percpumem 16 75 0 29 1 0 1 1 0 8 0
vcpupl 3904 14 0 1 2 0 2 2 0 8 0
vmpool 696 17 0 4 2 0 2 2 0 8 0
kstatmem 264 82 0 58 2 0 2 2 0 8 0
scsiplug 72 1 0 1 1 1 0 1 0 8 0
scxspl 216 25125 0 25125 13 12 1 8 1 8 1
plimitpl 152 153 0 135 1 0 1 1 0 8 0
sigapl 424 1610 0 1559 7 1 6 7 0 8 0
futexpl 64 15139 0 15139 4 3 1 1 0 8 1
knotepl 120 637 0 0 19 1 18 19 0 8 0
kqueuepl 216 311 0 303 1 0 1 1 0 8 0
pipepl 320 328 0 300 3 0 3 3 0 8 0
fdescpl 496 1590 0 1566 9 4 5 5 0 8 1
filepl 152 8413 0 8174 17 6 11 12 0 8 0
lockfpl 104 305 0 303 1 0 1 1 0 8 0
lockfspl 48 115 0 113 1 0 1 1 0 8 0
sessionpl 144 40 0 23 1 0 1 1 0 8 0
pgrppl 48 52 0 35 1 0 1 1 0 8 0
ucredpl 104 1132 0 1118 1 0 1 1 0 8 0
zombiepl 144 1566 0 1559 2 1 1 1 0 8 0
processpl 1136 1610 0 1559 4 0 4 4 0 8 0
procpl 656 2880 0 2805 8 1 7 8 0 8 0
srpgc 96 13 0 13 4 4 0 1 0 8 0
sosppl 168 25 0 25 9 9 0 1 0 8 0
sockpl 664 2306 0 2280 14 10 4 9 0 8 1
mcl64k 65536 6 0 0 1 0 1 1 0 8 0
mcl16k 16384 6 0 0 1 0 1 1 0 8 0
mcl12k 12288 7 0 0 1 0 1 1 0 8 0
mcl9k 9216 4 0 0 1 0 1 1 0 8 0
mcl8k 8192 12 0 0 2 0 2 2 0 8 0
mcl4k 4096 26 0 0 3 0 3 3 0 8 0
mcl2k2 2112 5 0 0 1 0 1 1 0 8 0
mcl2k 2048 311 0 0 39 0 39 39 0 8 0
mtagpl 96 3 0 0 1 0 1 1 0 8 0
mbufpl 256 1050 0 0 62 0 62 62 0 8 0
bufpl 280 9354 0 1882 534 0 534 534 0 8 0
anonpl 24 320372 0 309108 103 35 68 68 0 186 0
amapchunkpl 152 43655 0 42654 53 14 39 42 0 158 0
amappl16 200 7417 0 7288 36 26 10 20 0 8 0
amappl15 192 10 0 10 1 1 0 1 0 8 0
amappl14 184 206 0 188 2 1 1 2 0 8 0
amappl13 176 8 0 8 1 1 0 1 0 8 0
amappl12 168 2527 0 2491 3 1 2 2 0 8 0
amappl11 160 57 0 43 1 0 1 1 0 8 0
amappl10 152 100 0 86 1 0 1 1 0 8 0
amappl9 144 168 0 167 3 2 1 1 0 8 0
amappl8 136 370 0 283 4 0 4 4 0 8 0
amappl7 128 55 0 40 1 0 1 1 0 8 0
amappl6 120 604 0 582 2 1 1 2 0 8 0
amappl5 112 265 0 249 1 0 1 1 0 8 0
amappl4 104 693 0 651 4 2 2 4 0 8 0
amappl3 96 8732 0 8632 3 0 3 3 0 8 0
amappl2 88 2075 0 1991 4 2 2 4 0 8 0
amappl1 80 14957 0 14384 26 13 13 23 0 8 0
amappl 88 12778 0 12551 6 0 6 6 0 92 0
dma4096 4096 1 0 1 1 1 0 1 0 8 0
dma1024 1024 1 0 0 1 0 1 1 0 8 0
dma256 256 6 0 6 1 1 0 1 0 8 0
dma128 128 253 0 253 1 1 0 1 0 8 0
dma64 64 6 0 6 1 1 0 1 0 8 0
dma32 32 7 0 7 1 1 0 1 0 8 0
dma16 16 18 0 17 1 0 1 1 0 8 0
aobjpl 72 55 0 9 1 0 1 1 0 8 0
uaddrrnd 24 1608 0 1565 1 0 1 1 0 8 0
uaddrbest 32 2 0 0 1 0 1 1 0 8 0
uaddr 24 1608 0 1565 1 0 1 1 0 8 0
vmmpekpl 168 16023 0 15956 4 0 4 4 0 8 0
vmmpepl 168 120206 0 118040 148 45 103 122 0 357 0
vmsppl 440 1607 0 1564 6 1 5 5 0 8 0
rwobjpl 56 38957 0 33811 78 5 73 73 0 8 0
pdppl 4096 3223 0 3141 165 82 83 85 0 8 1
pvpl 32 49113 0 0 398 1 397 397 0 265 0
pmappl 248 1607 0 1564 3 0 3 3 0 8 0
extentpl 40 56 0 38 1 0 1 1 0 8 0
phpool 112 530 0 103 13 0 13 13 0 8 0
ddb{1}> machine ddbcpu 0
Stopped at x86_ipi_db+0x1e: addq $0x8,%rsp
x86_ipi_db(ffffffff82cddff0) at x86_ipi_db+0x1e sys/arch/amd64/amd64/db_interface.c:393
x86_ipi_handler() at x86_ipi_handler+0xb7 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
pagezero() at pagezero+0x1c
end trace frame: 0x0, count: 11
ddb{0}> trace
x86_ipi_db(ffffffff82cddff0) at x86_ipi_db+0x1e sys/arch/amd64/amd64/db_interface.c:393
x86_ipi_handler() at x86_ipi_handler+0xb7 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
pagezero() at pagezero+0x1c
end trace frame: 0x0, count: -4
ddb{0}> machine ddbcpu 1
Stopped at VOP_LOCK+0x72: movq 0(%rax),%r14
VOP_LOCK(fffffd807d4db6f8,41) at VOP_LOCK+0x72 sys/kern/vfs_vops.c:515
vn_lock(fffffd807d4db6f8,41) at vn_lock+0x85 sys/kern/vfs_vnops.c:564
vget(fffffd807d4db6f8,41) at vget+0x1fd sys/kern/vfs_subr.c:676
syncer_thread(ffff80002a148a48) at syncer_thread+0xbd sys/kern/vfs_sync.c:150
end trace frame: 0x0, count: 11
ddb{1}> trace
VOP_LOCK(fffffd807d4db6f8,41) at VOP_LOCK+0x72 sys/kern/vfs_vops.c:515
vn_lock(fffffd807d4db6f8,41) at vn_lock+0x85 sys/kern/vfs_vnops.c:564
vget(fffffd807d4db6f8,41) at vget+0x1fd sys/kern/vfs_subr.c:676
syncer_thread(ffff80002a148a48) at syncer_thread+0xbd sys/kern/vfs_sync.c:150
end trace frame: 0x0, count: -4


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