syzbot
KASAN: invalid memory access in mtx_leave
Status:
fixed on 2026/09/04 02:14
Reported-by: syzbot+bf11bb99176436b58ec5@syzkaller.appspotmail.com
Fix commit:
53d74301dd9a
Close mtx_wantipl race in mtx_leave
First crash: 21d, last: 21d
Sample crash report:
panic: Caught invalid memory access at ffff800034aebaf8 size 4 op 0
Stopped at db_enter+0x17: popq %rbp
TID PID UID PRFLAGS PFLAGS CPU COMMAND
*390033 76491 0 0x14000 0x200 0 reaper
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff8463b860) at panic+0x270 sys/kern/subr_prf.c:198
__asan_load4_noabort(ffff800034aebaf8) at __asan_load4_noabort+0xa3
mtx_leave(ffff800034aebaf0) at mtx_leave+0x295 sys/kern/kern_lock.c:532
reaper(ffff8000298954c8) at reaper+0x4e5 sys/kern/kern_exit.c:527
end trace frame: 0x0, count: 10
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{0}>
ddb{0}> set $lines = 0
ddb{0}> set $maxwidth = 0
ddb{0}> show panic
*cpu0: Caught invalid memory access at ffff800034aebaf8 size 4 op 0
ddb{0}> show kasan
KASAN: invalid read of 4 bytes at 0xffff800034aebaf8 from pc 0xffffffff82d15ec5
KASAN: first bad byte at 0xffff800034aebaf8 (+0); shadow 0x08: valid
KASAN: 0xffff800034aebaf8 is 272 bytes inside the 1232-byte item [0xffff800034aeb9e8..0xffff800034aebeb8) in pool 'processpl'
KASAN: allocated at:
#0 pool_get+0x770 sys/kern/subr_pool.c:834
#1 process_new+0x47 sys/kern/kern_fork.c:221
#2 fork1+0x533 sys/kern/kern_fork.c:408
#3 syscall+0x1089 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#3 syscall+0x1089 sys/arch/amd64/amd64/trap.c:791
#4 Xsyscall+0x128
KASAN: freed at:
#0 pool_put+0x79 sys/kern/subr_pool.c:1019
#1 process_zap+0x46c sys/kern/kern_exit.c:912
#2 dowait6+0x10dd sys/kern/kern_exit.c:589
#3 sys_wait4+0x244 sys/kern/kern_exit.c:730
#4 syscall+0x1089 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#4 syscall+0x1089 sys/arch/amd64/amd64/trap.c:791
#5 Xsyscall+0x128
KASAN: pc: mtx_leave+0x295
KASAN: call trace:
#0 __asan_load4_noabort+0x82 kasan_shadow_check sys/kern/subr_kasan.c:1014 [inline]
#0 __asan_load4_noabort+0x82 sys/kern/subr_kasan.c:1098
#1 mtx_leave+0x295 sys/kern/kern_lock.c:532
#2 reaper+0x4e5 sys/kern/kern_exit.c:527
#3 proc_trampoline+0x10
KASAN: shadow of 0xffff800034aeb980..0xffff800034aebc00 (1 cell = 8 bytes):
0xffff800034aeb980: 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08
0xffff800034aeba00: 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08
>0xffff800034aeba80: 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08[08]
0xffff800034aebb00: 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08
0xffff800034aebb80: 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08 08
KASAN: legend: 00 valid; 01..07 partial; fb malloc redzone; fc malloc freed; fd pool freed; fe kmem; fa global; f1..f4/f8 stack/scope
ddb{0}> trace
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff8463b860) at panic+0x270 sys/kern/subr_prf.c:198
__asan_load4_noabort(ffff800034aebaf8) at __asan_load4_noabort+0xa3
mtx_leave(ffff800034aebaf0) at mtx_leave+0x295 sys/kern/kern_lock.c:532
reaper(ffff8000298954c8) at reaper+0x4e5 sys/kern/kern_exit.c:527
end trace frame: 0x0, count: -5
ddb{0}> show registers
rdi 0
rsi 0x1
rbp 0xffff800029893610
rbx 0xffff800029893680
rdx 0
rcx 0xffffffff85355ff0 cpu_info_full_primary+0x1ff0
rax 0
r8 0x101010101010101
r9 0x8080808080808080
r10 0x21
r11 0xffffffff816a3620 x86_bus_space_io_read_1
r12 0xffffffff8463b860 .str.7+0x9be80
r13 0xffffffff85356c08 cpu_info_full_primary+0x2c08
r14 0xffffffff85356e07 cpu_info_full_primary+0x2e07
r15 0x1
rip 0xffffffff84365cd7 db_enter+0x17
cs 0x8
rflags 0x246
rsp 0xffff800029893610
ss 0
db_enter+0x17: popq %rbp
ddb{0}> show proc
PROC (reaper) tid=390033 pid=76491 tcnt=1 stat=onproc
flags process=14000<NOZOMBIE,SYSTEM> proc=200<SYSTEM>
runpri=4, usrpri=51, slppri=4, nice=20
wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
forw=0xffffffffffffffff, list=0xffff800045fffc88,0xffff800029895240
process=0xffff800029803020 user=0xffff800029888000, vmspace=0xffffffff854cdfa0
estcpu=1, cpticks=39, pctcpu=0.1, user=0, sys=0, intr=0
ddb{0}> ps
PID TID PPID UID S PRLAGS PFLAGS WAIT COMMAND
1165 245887 76695 0 3 0x100002 0x88 sigsusp sh
82170 117316 95107 0 2 0x100000 0 sh
95107 503730 43701 0 3 0x100002 0x88 sigsusp sh
18527 517636 57847 0 3 0x100002 0x88 sigsusp sh
37428 331779 94715 0 2 0x2 0 sh
94715 38521 52944 0 3 0x2 0x80 wait syz-executor
76695 31244 52944 0 3 0x2 0x80 wait syz-executor
43701 399497 52944 0 3 0x2 0x80 wait syz-executor
57847 287908 52944 0 3 0x2 0x80 wait syz-executor
12777 232158 52944 0 3 0x2 0x80 nanoslp syz-executor
70670 321203 0 0 3 0x14000 0x280 nfsidl nfsio
36126 145599 0 0 3 0x14000 0x280 nfsidl nfsio
86813 111293 0 0 3 0x14000 0x280 nfsidl nfsio
7853 150846 0 0 3 0x14000 0x280 nfsidl nfsio
60573 340709 0 0 3 0x14000 0x280 nfsidl nfsio
35356 94246 0 0 3 0x14000 0x280 nfsidl nfsio
53260 67823 0 0 3 0x14000 0x280 nfsidl nfsio
15089 85308 0 0 3 0x14000 0x280 nfsidl nfsio
55806 208870 0 0 3 0x14000 0x280 nfsidl nfsio
90284 25711 0 0 3 0x14000 0x280 nfsidl nfsio
15661 395172 0 0 3 0x14000 0x280 nfsidl nfsio
67767 146152 0 0 3 0x14000 0x280 nfsidl nfsio
17812 310743 0 0 3 0x14000 0x280 nfsidl nfsio
79406 307100 0 0 3 0x14000 0x280 nfsidl nfsio
9301 67573 0 0 3 0x14000 0x280 nfsidl nfsio
21057 191600 0 0 3 0x14000 0x280 nfsidl nfsio
12371 350578 0 0 3 0x14000 0x280 nfsidl nfsio
10924 31195 0 0 3 0x14000 0x280 nfsidl nfsio
8859 421627 0 0 3 0x14000 0x280 nfsidl nfsio
37463 3310 0 0 3 0x14000 0x280 nfsidl nfsio
55424 231081 0 0 3 0x14000 0x200 acct acct
52944 476727 60142 0 3 0x2 0x80 nanoslp syz-executor
60142 303997 92083 0 3 0x100002 0x88 sigsusp ksh
92083 201705 8222 0 3 0x10 0x88 kqread sshd-session
8222 380274 9641 0 3 0x12 0x80 kqread sshd-session
60235 169880 1 0 3 0x100003 0x80 ttyin getty
9641 150191 1 0 3 0 0x88 kqread sshd
6156 364270 17533 74 3 0x1100012 0x80 bpf pflogd
17533 237866 1 0 3 0 0x80 sbwait pflogd
80447 245545 84576 73 3 0x1100010 0x80 kqread syslogd
84576 34629 1 0 3 0x100002 0x80 sbwait syslogd
7848 349868 1 0 3 0x100000 0x80 kqread resolvd
69856 222927 98031 77 3 0x100012 0x80 kqread dhcpleased
53254 85916 98031 77 3 0x100012 0x80 kqread dhcpleased
98031 83269 1 0 3 0 0x80 kqread dhcpleased
30255 486058 0 0 3 0x14000 0x200 bored smr
90006 432903 0 0 2 0x14000 0x200 zerothread
41284 521242 0 0 3 0x14000 0x200 aiodoned aiodoned
45348 476601 0 0 3 0x14000 0x200 syncer update
63579 297732 0 0 3 0x14000 0x200 cleaner cleaner
*76491 390033 0 0 7 0x14000 0x200 reaper
83705 367431 0 0 3 0x14000 0x200 pgdaemon pagedaemon
77694 442513 0 0 3 0x14000 0x200 bored viomb
18449 221346 0 0 3 0x14000 0x40000200 acpi0 acpi0
96174 461254 0 0 7 0x14000 0x40000200 idle1
34021 93904 0 0 3 0x14000 0x200 bored softnet1
9286 252378 0 0 3 0x14000 0x200 bored softnet0
86844 489623 0 0 3 0x14000 0x200 smrbar systqmp
44159 121766 0 0 3 0x14000 0x200 bored systq
82617 485255 0 0 3 0x14000 0x200 tmoslp softclockmp
65903 225780 0 0 3 0x14000 0x40000200 tmoslp softclock
2076 264413 0 0 3 0x14000 0x40000200 idle0
1 442434 0 0 3 0x2 0x80 wait init
0 0 -1 0 3 0x10000 0x200 scheduler swapper
ddb{0}> show all locks
CPU 0:
exclusive mutex /syzkaller/managers/kasan/kernel/sys/kern/kern_event.c:210 r = 0 (0xffffffff851fa250)
#0 witness_lock+0x632 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x632 sys/kern/subr_witness.c:1160
#1 mtx_enter+0x683 sys/kern/kern_lock.c:487
#2 reaper+0x32d sys/kern/kern_exit.c:511
#3 proc_trampoline+0x10
Process 86844 (systqmp) thread 0xffff800045ffe000 (489623)
shared rwlock systqmp r = 0 (0xffffffff85063f78)
#0 witness_lock+0x632 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x632 sys/kern/subr_witness.c:1160
#1 taskq_thread+0x1ba sys/kern/kern_task.c:442
#2 proc_trampoline+0x10
ddb{0}> show malloc
Type InUse MemUse HighUse Limit Requests Type Lim
devbuf 11046 12237K 12533K 166960K 12624 0
pcb 17 28K 30K 166960K 58 0
rtable 139 7K 13K 166960K 2703 0
pf 28 20K 23K 166960K 224 0
ifaddr 27 8K 13K 166960K 372 0
ifgroup 43 2K 2K 166960K 397 0
sysctl 1 1K 13K 166960K 7 0
counters 64 41K 43K 166960K 240 0
ioctlops 0 0K 4K 166960K 1600 0
iov 0 0K 4K 166960K 7 0
mount 1 1K 1K 166960K 1 0
log 0 0K 0K 166960K 4 0
vnodes 1352 87K 87K 166960K 2512 0
UFS quota 1 36K 36K 166960K 1 0
UFS mount 5 44K 44K 166960K 5 0
shm 2 2K 6K 166960K 6 0
VM map 2 1K 1K 166960K 2 0
sem 7 0K 0K 166960K 8 0
dirhash 15 2K 2K 166960K 15 0
ACPI 1734 201K 292K 166960K 11964 0
file desc 13 45K 93K 166960K 1547 0
sigio 0 0K 0K 166960K 1 0
proc 71 128K 210K 166960K 2791 0
subproc 45 5K 9K 166960K 792 0
NFS srvsock 1 0K 0K 166960K 1 0
NFS daemon 1 20K 20K 166960K 1 0
ip_moptions 0 0K 0K 166960K 6 0
in_multi 46 3K 7K 166960K 959 0
ether_multi 1 0K 0K 166960K 1 0
mrt 0 0K 0K 166960K 21 0
ISOFS mount 1 36K 36K 166960K 1 0
MSDOSFS mount 1 20K 20K 166960K 1 0
ttys 55 384K 384K 166960K 55 0
exec 0 0K 2K 166960K 1416 0
fusefs mount 1 36K 36K 166960K 1 0
tdb 3 1K 1K 166960K 3 0
VM swap 14 124K 124K 166960K 15 0
UVM amap 173 223K 279K 166960K 11432 0
UVM aobj 15 12K 12K 166960K 18 0
pinsyscall 1062 1747K 1818K 166960K 4759 0
memdesc 1 4K 4K 166960K 1 0
crypto data 1 1K 1K 166960K 1 0
ip6_options 0 0K 0K 166960K 1 0
NDP 13 0K 2K 166960K 269 0
temp 22 9165K 9186K 166960K 14579 0
kqueue 13 40K 68K 166960K 64 0
SYN cache 2 16K 16K 166960K 2 0
ddb{0}> show all pools
Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
plcache 128 28 0 0 1 0 1 1 0 8 0
rtpcb 120 194 0 191 1 0 1 1 0 8 0
rtentry 176 975 0 914 7 2 5 6 0 8 2
unpcb 144 777 0 760 4 0 4 4 0 8 3
syncache 336 4 0 4 1 1 0 1 0 8 0
sackhl 24 1 0 1 1 1 0 1 0 8 0
tcpcb 736 169 0 165 7 6 1 7 0 8 0
arp 136 177 0 166 1 0 1 1 0 8 0
inpcb 328 1247 0 1240 7 0 7 7 0 8 6
nd6 152 257 0 249 1 0 1 1 0 8 0
kcovpl 48 88 0 83 1 0 1 1 0 8 0
ppxss 1192 1 0 1 1 1 0 1 0 8 0
pffrag 232 3 0 0 1 0 1 1 0 482 0
pffrnode 88 3 0 0 1 0 1 1 0 8 0
pffrent 40 3 0 0 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 35 0 8 1 0 1 1 0 8 0
pfstkey 128 35 0 8 1 0 1 1 0 8 0
pfstate 448 35 0 8 4 0 4 4 0 8 0
pfrule 1360 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 3934 0 3645 40 14 26 29 0 8 7
art_table 40 3935 0 3645 6 1 5 5 0 8 1
art_node 32 975 0 917 1 0 1 1 0 8 0
semapl 72 6 0 1 1 0 1 1 0 8 0
shmpl 112 15 0 3 1 0 1 1 0 8 0
dirhash 1024 19 0 0 3 0 3 3 0 8 0
dino2pl 256 2001 0 369 102 0 102 102 0 8 0
ffsino 296 2001 0 369 126 0 126 126 0 8 0
nchpl 144 2536 0 515 75 0 75 75 0 8 0
vnodes 216 3174 0 0 177 0 177 177 0 8 0
namei 1024 16136 0 16136 2 1 1 2 0 8 1
percpumem 16 136 0 88 1 0 1 1 0 8 0
kstatmem 264 197 0 176 2 0 2 2 0 8 0
scxspl 216 8981 0 8981 5 4 1 3 1 8 1
plimitpl 152 222 0 206 1 0 1 1 0 8 0
sigapl 424 1725 0 1657 9 0 9 9 0 8 1
knotepl 120 94 0 0 3 0 3 3 0 8 0
kqueuepl 224 226 0 217 5 4 1 5 0 8 0
pipepl 344 393 0 366 4 1 3 4 0 8 0
fdescpl 528 1688 0 1661 3 0 3 3 0 8 0
filepl 160 7090 0 6919 18 3 15 16 0 8 6
lockfpl 104 59 0 57 1 0 1 1 0 8 0
lockfspl 48 30 0 28 1 0 1 1 0 8 0
sessionpl 144 197 0 188 1 0 1 1 0 8 0
pgrppl 48 286 0 270 1 0 1 1 0 8 0
ucredpl 104 428 0 415 1 0 1 1 0 8 0
zombiepl 144 1662 0 1657 1 0 1 1 0 8 0
processpl 1232 1725 0 1657 6 0 6 6 0 8 0
procpl 664 2243 0 2175 8 1 7 8 0 8 0
sockpl 752 2223 0 2196 51 40 11 17 0 8 8
mcl64k 65536 1 0 0 1 0 1 1 0 8 0
mcl8k 8192 3 0 0 1 0 1 1 0 8 0
mcl4k 4096 124 0 0 16 0 16 16 0 8 0
mcl2k 2048 22 0 0 3 0 3 3 0 8 0
mextrefs 64 21 0 0 1 0 1 1 0 8 0
mtagpl 96 3 0 0 1 0 1 1 0 8 0
mbufpl 256 155 0 0 10 0 10 10 0 8 0
bufpl 272 2740 0 106 176 0 176 176 0 8 0
anonpl 32 3841 0 0 31 0 31 31 0 222 0
amapchunkpl 152 30074 0 29777 23 6 17 22 0 158 2
amappl16 200 2195 0 2187 5 4 1 5 0 8 0
amappl15 192 6 0 6 1 1 0 1 0 8 0
amappl14 184 1383 0 1378 1 0 1 1 0 8 0
amappl13 176 281 0 268 1 0 1 1 0 8 0
amappl12 168 2252 0 2226 2 0 2 2 0 8 0
amappl11 160 3 0 3 1 1 0 1 0 8 0
amappl10 152 69 0 53 1 0 1 1 0 8 0
amappl9 144 270 0 269 1 0 1 1 0 8 0
amappl8 136 414 0 412 1 0 1 1 0 8 0
amappl7 128 305 0 292 1 0 1 1 0 8 0
amappl6 120 950 0 943 1 0 1 1 0 8 0
amappl5 112 100 0 90 1 0 1 1 0 8 0
amappl4 104 540 0 520 1 0 1 1 0 8 0
amappl3 96 5843 0 5777 3 0 3 3 0 8 0
amappl2 88 1494 0 1424 2 0 2 2 0 8 0
amappl1 80 21430 0 20852 16 2 14 15 0 8 1
amappl 88 9352 0 9250 5 0 5 5 0 92 0
uvmvnodes 80 106 0 0 3 0 3 3 0 8 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 17 0 3 1 0 1 1 0 8 0
uaddrrnd 24 1688 0 1661 1 0 1 1 0 8 0
uaddrbest 32 2 0 0 1 0 1 1 0 8 0
uaddr 24 1688 0 1661 1 0 1 1 0 8 0
vmmpekpl 168 15013 0 14965 3 0 3 3 0 8 0
vmmpepl 168 115583 0 114020 87 7 80 87 0 357 3
vmsppl 488 1687 0 1659 5 0 5 5 0 8 1
rwobjpl 80 34296 0 33335 26 3 23 25 0 8 0
pdppl 4096 3384 0 3318 188 120 68 86 0 8 2
pvpl 32 10404 0 0 85 1 84 84 0 265 0
pmappl 256 1687 0 1659 3 0 3 3 0 8 0
extentpl 40 47 0 29 1 0 1 1 0 8 0
phpool 120 563 0 145 13 0 13 13 0 8 0
ddb{0}> machine ddbcpu 0
Invalid cpu 0
ddb{0}> trace
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff8463b860) at panic+0x270 sys/kern/subr_prf.c:198
__asan_load4_noabort(ffff800034aebaf8) at __asan_load4_noabort+0xa3
mtx_leave(ffff800034aebaf0) at mtx_leave+0x295 sys/kern/kern_lock.c:532
reaper(ffff8000298954c8) at reaper+0x4e5 sys/kern/kern_exit.c:527
end trace frame: 0x0, count: -5
ddb{0}> machine ddbcpu 1
Stopped at x86_ipi_db+0x19: leave
x86_ipi_db(ffff800028fe3ff0) at x86_ipi_db+0x19 sys/arch/amd64/amd64/db_interface.c:412
x86_ipi_handler() at x86_ipi_handler+0x112 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
acpicpu_idle() at acpicpu_idle+0x63c sys/dev/acpi/acpicpu_x86.c:-1
sched_idle(ffff800028fe3ff0) at sched_idle+0x566 sys/kern/kern_sched.c:204
end trace frame: 0x0, count: 10
ddb{1}> trace
x86_ipi_db(ffff800028fe3ff0) at x86_ipi_db+0x19 sys/arch/amd64/amd64/db_interface.c:412
x86_ipi_handler() at x86_ipi_handler+0x112 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
acpicpu_idle() at acpicpu_idle+0x63c sys/dev/acpi/acpicpu_x86.c:-1
sched_idle(ffff800028fe3ff0) at sched_idle+0x566 sys/kern/kern_sched.c:204
end trace frame: 0x0, count: -5
Struck through repros no longer work on HEAD.