syzbot
uvm_fault: sys_shmat (3)
Status:
upstream: reported on 2026/06/24 23:01
Reported-by: syzbot+f5d2ec16c4993e11ed9e@syzkaller.appspotmail.com
First crash: 107d, last: 2h27m
Sample crash report:
uvm_fault(0xfffffa006d181e70, 0x0, 0, 1) -> e
kernel: page fault trap, code=0
Stopped at sys_shmat+0x39d: movq 0(%r14),%rdi
TID PID UID PRFLAGS PFLAGS CPU COMMAND
*240541 19358 0 0 0x4000000 0 syz-executor
sys_shmat(ffff80002a7382c0,ffff80002b0d5ed0,ffff80002b0d5e20) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002b0d5ed0) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002b0d5ed0) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xec348594810, count: 12
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>
ddb> set $lines = 0
ddb> set $maxwidth = 0
ddb> show panic
*cpu0: uvm_fault(0xfffffa006d181e70, 0x0, 0, 1) -> e
ddb> show kasan
No such command
ddb> trace
sys_shmat(ffff80002a7382c0,ffff80002b0d5ed0,ffff80002b0d5e20) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002b0d5ed0) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002b0d5ed0) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xec348594810, count: -3
ddb> show registers
rdi 0
rsi 0
rbp 0xffff80002b0d5e00
rbx 0
rdx 0x1
rcx 0x1
rax 0xfffffa006896df00
r8 0x180
r9 0xfffffa0007ffd750
r10 0x53fd86ca46bd335a
r11 0x316aad5d77447579
r12 0xffff80002a7382c0
r13 0xffff8000015f6000
r14 0
r15 0x3
rip 0xffffffff830dfabd sys_shmat+0x39d
cs 0x8
rflags 0x10246 __ALIGN_SIZE+0xf246
rsp 0xffff80002b0d5d70
ss 0x10
sys_shmat+0x39d: movq 0(%r14),%rdi
ddb> show proc
PROC (syz-executor) tid=240541 pid=19358 tcnt=4 stat=onproc
flags process=0 proc=4000000<THREAD>
runpri=75, usrpri=75, slppri=32, nice=20
wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
forw=0xffffffffffffffff, list=0xffff80002a739780,0xffff80002a738d30
process=0xffff80002a89f1f8 user=0xffff80002b0d0000, vmspace=0xfffffa006d181e70
estcpu=25, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb> ps
PID TID PPID UID S PRLAGS PFLAGS WAIT COMMAND
56210 156593 70572 0 2 0 0 syz-executor
56210 318930 70572 0 2 0 0x4000000 syz-executor
19358 190332 81690 0 2 0 0 syz-executor
19358 111149 81690 0 3 0 0x4000080 fsleep syz-executor
19358 39984 81690 0 2 0 0x4000000 syz-executor
*19358 240541 81690 0 7 0 0x4000000 syz-executor
95528 501587 55147 0 2 0 0 syz-executor
95528 10286 55147 0 3 0 0x4000080 fsleep syz-executor
40259 252223 72368 0 2 0 0 syz-executor
40259 289537 72368 0 3 0 0x4000080 kqsel syz-executor
40259 33090 72368 0 2 0 0x4000000 syz-executor
40259 466959 72368 0 2 0 0x4000000 syz-executor
25745 242557 14431 0 2 0 0 syz-executor
25745 411638 14431 0 3 0 0x4000080 fsleep syz-executor
51333 42500 81085 0 2 0 0 syz-executor
51333 402962 81085 0 2 0 0x4000000 syz-executor
51333 308141 81085 0 3 0 0x4000080 fsleep syz-executor
51333 35797 81085 0 2 0 0x4000000 syz-executor
49271 385579 43602 0 2 0x2 0 syz-executor
81085 113906 43602 0 3 0x2 0x80 nanoslp syz-executor
55147 481417 43602 0 3 0x2 0x80 nanoslp syz-executor
72368 453047 43602 0 3 0x2 0x80 nanoslp syz-executor
70572 44841 43602 0 3 0x2 0x80 nanoslp syz-executor
81690 344609 43602 0 3 0x2 0x80 nanoslp syz-executor
96680 496594 43602 0 3 0x2 0x80 wait syz-executor
14431 491626 43602 0 3 0x2 0x80 nanoslp syz-executor
43602 300377 62315 0 2 0x2 0 syz-executor
62315 158412 1277 0 3 0x100002 0x88 sigsusp ksh
1277 29442 5658 0 3 0x10 0x88 kqread sshd-session
5658 440792 40978 0 3 0x12 0x80 kqread sshd-session
60661 480935 1 0 3 0x100003 0x80 ttyin getty
40978 262342 1 0 3 0 0x88 kqread sshd
34049 208539 33331 73 3 0x1100010 0x80 kqread syslogd
33331 459508 1 0 3 0x100002 0x80 sbwait syslogd
16867 227969 1 0 3 0x100000 0x80 kqread resolvd
15288 171754 67486 77 3 0x100012 0x80 kqread dhcpleased
8126 250551 67486 77 3 0x100012 0x80 kqread dhcpleased
67486 241655 1 0 3 0 0x80 kqread dhcpleased
5061 99973 0 0 3 0x14000 0x200 bored smr
32722 162169 0 0 2 0x14000 0x200 zerothread
99955 38601 0 0 3 0x14000 0x200 aiodoned aiodoned
46362 440686 0 0 3 0x14000 0x200 syncer update
48671 282385 0 0 3 0x14000 0x200 cleaner cleaner
25518 477544 0 0 3 0x14000 0x200 reaper reaper
77244 47742 0 0 3 0x14000 0x200 pgdaemon pagedaemon
57555 399575 0 0 3 0x14000 0x200 bored viomb
79701 37110 0 0 3 0x14000 0x40000200 acpi0 acpi0
21865 445388 0 0 3 0x14000 0x200 bored softnet0
59680 19425 0 0 3 0x14000 0x200 bored systqmp
31626 367708 0 0 3 0x14000 0x200 bored systq
6734 147684 0 0 3 0x14000 0x40000200 tmoslp softclock
65378 95127 0 0 3 0x14000 0x40000200 idle0
1 357139 0 0 3 0x2 0x80 wait init
0 0 -1 0 3 0x10000 0x200 scheduler swapper
ddb> show all locks
No such command
ddb> show malloc
Type InUse MemUse HighUse Limit Requests Type Lim
devbuf 11028 12103K 12119K 166960K 12224 0
pcb 17 14K 16K 166960K 110 0
rtable 215 5K 6K 166960K 775 0
pf 29 12K 13K 166960K 59 0
ifaddr 38 6K 7K 166960K 102 0
ifgroup 46 2K 2K 166960K 106 0
sysctl 1 1K 9K 166960K 5 0
counters 32 17K 17K 166960K 47 0
ioctlops 0 0K 4K 166960K 52 0
iov 0 0K 12K 166960K 3 0
mount 1 1K 1K 166960K 1 0
log 0 0K 0K 166960K 4 0
vnodes 1289 81K 81K 166960K 1533 0
UFS quota 1 32K 32K 166960K 1 0
UFS mount 5 36K 36K 166960K 5 0
shm 3 5K 5K 166960K 3 0
VM map 2 1K 1K 166960K 2 0
sem 4 0K 0K 166960K 5 0
dirhash 12 2K 2K 166960K 15 0
ACPI 1692 195K 286K 166960K 12470 0
file desc 17 61K 97K 166960K 421 0
sigio 0 0K 0K 166960K 70 0
proc 60 59K 124K 166960K 893 0
subproc 66 4K 4K 166960K 201 0
NFS srvsock 1 0K 0K 166960K 1 0
NFS daemon 1 16K 16K 166960K 1 0
ip_moptions 0 0K 0K 166960K 6 0
in_multi 88 5K 6K 166960K 257 0
ether_multi 1 0K 0K 166960K 2 0
mrt 0 0K 0K 166960K 9 0
ISOFS mount 1 32K 32K 166960K 1 0
MSDOSFS mount 1 16K 16K 166960K 1 0
ttys 49 228K 228K 166960K 49 0
exec 0 0K 2K 166960K 552 0
fusefs mount 1 32K 32K 166960K 1 0
tdb 3 0K 0K 166960K 3 0
VM swap 8 62K 64K 166960K 10 0
UVM amap 226 143K 159K 166960K 4820 0
UVM aobj 3 2K 6K 166960K 5 0
pinsyscall 38 76K 96K 166960K 1885 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 12 0K 2K 166960K 69 0
temp 35 9114K 9178K 166960K 6078 0
kqueue 13 20K 22K 166960K 31 0
SYN cache 2 16K 16K 166960K 2 0
ddb> show all pools
Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
rtpcb 120 70 0 67 1 0 1 1 0 8 0
rtentry 136 266 0 167 4 0 4 4 0 8 0
unpcb 144 94 0 79 2 0 2 2 0 8 1
syncache 336 4 0 4 1 1 0 1 0 8 0
tcpcb 736 23 0 19 1 0 1 1 0 8 0
arp 96 46 0 30 1 0 1 1 0 8 0
inpcb 328 338 0 327 10 6 4 7 0 8 3
nd6 112 67 0 46 1 0 1 1 0 8 0
kcovpl 48 22 0 15 1 0 1 1 0 8 0
pfstscr 40 1 0 0 1 0 1 1 0 8 0
pfstitem 24 2 0 0 1 0 1 1 0 8 0
pfstkey 128 2 0 0 1 0 1 1 0 8 0
pfstate 384 1 0 0 1 0 1 1 0 8 0
art_heap8 4096 1 0 0 1 0 1 1 0 8 0
art_heap4 256 1080 0 669 32 1 31 32 0 8 4
art_table 40 1081 0 669 6 0 6 6 0 8 1
art_node 32 266 0 176 1 0 1 1 0 8 0
sysvmsgpl 40 105 0 65 1 0 1 1 0 8 0
semapl 72 3 0 1 1 0 1 1 0 8 0
shmpl 120 1 0 0 1 0 1 1 0 8 0
dirhash 1024 19 0 2 3 0 3 3 0 8 0
dino2pl 256 1728 0 231 94 0 94 94 0 8 0
ffsino 256 1728 0 231 94 0 94 94 0 8 0
nchpl 144 2039 0 281 66 0 66 66 0 8 0
vnodes 216 1952 0 0 109 0 109 109 0 8 0
namei 1024 8690 0 8689 5 3 2 4 0 8 1
vcpupl 3968 32 0 32 4 4 0 4 0 8 0
vmpool 808 2 0 2 1 1 0 1 0 8 0
kstatmem 264 51 0 30 2 0 2 2 0 8 0
scxspl 216 6774 0 6774 6 3 3 4 1 8 3
plimitpl 152 52 0 36 1 0 1 1 0 8 0
sigapl 424 686 0 644 7 1 6 6 0 8 1
knotepl 120 4835 0 4787 15 5 10 10 0 8 8
kqueuepl 184 222 0 208 4 0 4 4 0 8 3
pipepl 304 171 0 144 3 0 3 3 0 8 0
fdescpl 448 673 0 644 5 1 4 5 0 8 0
filepl 120 2758 0 2550 10 1 9 9 0 8 1
lockfpl 104 12 0 10 1 0 1 1 0 8 0
lockfspl 48 7 0 5 1 0 1 1 0 8 0
sessionpl 144 38 0 30 1 0 1 1 0 8 0
pgrppl 48 61 0 45 1 0 1 1 0 8 0
ucredpl 104 157 0 144 1 0 1 1 0 8 0
zombiepl 144 731 0 730 1 0 1 1 0 8 0
processpl 1160 686 0 644 5 1 4 4 0 8 0
procpl 664 872 0 818 7 1 6 6 0 8 1
sockpl 552 505 0 475 9 4 5 7 0 8 2
mcl8k 8192 4 0 4 1 1 0 1 0 8 0
mcl4k 4096 2549 0 2488 14 5 9 14 0 8 0
mcl2k 2048 422 0 422 4 1 3 3 0 8 3
mextrefs 64 121 0 121 2 1 1 1 0 8 1
mtagpl 96 4 0 4 1 1 0 1 0 8 0
mbufpl 256 6375 0 6173 18 0 18 18 0 8 1
bufpl 272 2420 0 102 155 0 155 155 0 8 0
anonpl 24 102791 0 99708 32 1 31 31 0 187 10
amapchunkpl 152 25498 0 24997 38 3 35 35 0 158 15
amappl16 200 1271 0 1254 6 3 3 4 0 8 2
amappl15 192 4 0 4 1 1 0 1 0 8 0
amappl14 184 575 0 574 1 0 1 1 0 8 0
amappl13 176 144 0 134 1 0 1 1 0 8 0
amappl12 168 966 0 938 2 0 2 2 0 8 0
amappl11 160 7 0 7 1 1 0 1 0 8 0
amappl10 152 58 0 48 1 0 1 1 0 8 0
amappl9 144 274 0 274 1 1 0 1 0 8 0
amappl8 136 152 0 151 1 0 1 1 0 8 0
amappl7 128 171 0 160 1 0 1 1 0 8 0
amappl6 120 298 0 297 1 0 1 1 0 8 0
amappl5 112 91 0 83 1 0 1 1 0 8 0
amappl4 104 304 0 289 1 0 1 1 0 8 0
amappl3 96 2395 0 2300 4 1 3 3 0 8 0
amappl2 88 743 0 672 2 0 2 2 0 8 0
amappl1 80 12123 0 11571 14 1 13 13 0 8 1
amappl 88 3892 0 3727 5 0 5 5 0 92 0
uvmvnodes 80 98 0 0 2 0 2 2 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 5 0 2 1 0 1 1 0 8 0
uaddrrnd 24 673 0 644 1 0 1 1 0 8 0
uaddrbest 32 2 0 0 1 0 1 1 0 8 0
uaddr 24 673 0 644 1 0 1 1 0 8 0
vmmpekpl 168 7127 0 7081 3 0 3 3 0 8 0
vmmpepl 168 51950 0 50178 86 5 81 81 0 357 3
vmsppl 368 672 0 644 4 1 3 4 0 8 0
rwobjpl 40 17526 0 16583 11 0 11 11 0 8 0
pdppl 4096 1356 0 1292 108 44 64 82 0 8 0
pvpl 32 278950 0 271015 90 3 87 87 0 265 19
pmappl 216 674 0 646 3 1 2 3 0 8 0
extentpl 40 45 0 27 1 0 1 1 0 8 0
phpool 112 544 0 61 14 0 14 14 0 8 0
ddb> machine ddbcpu 0
No such command
ddb> trace
sys_shmat(ffff80002a7382c0,ffff80002b0d5ed0,ffff80002b0d5e20) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002b0d5ed0) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002b0d5ed0) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xec348594810, count: -3
ddb> machine ddbcpu 1
No such command
ddb> trace
sys_shmat(ffff80002a7382c0,ffff80002b0d5ed0,ffff80002b0d5e20) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002b0d5ed0) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002b0d5ed0) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xec348594810, count: -3
Struck through repros no longer work on HEAD.