syzbot
uvm_fault: sys_shmat (3)
Status:
upstream: reported on 2026/06/24 23:01
Reported-by: syzbot+f5d2ec16c4993e11ed9e@syzkaller.appspotmail.com
First crash: 101d, last: 25m
Sample crash report:
uvm_fault(0xfffff1006c4ff468, 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
*321914 68614 0 0 0x4000000 0 syz-executor
sys_shmat(ffff80002a738fb8,ffff80002a83d660,ffff80002a83d5b0) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002a83d660) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a83d660) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f27ad06490, 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(0xfffff1006c4ff468, 0x0, 0, 1) -> e
ddb> show kasan
No such command
ddb> trace
sys_shmat(ffff80002a738fb8,ffff80002a83d660,ffff80002a83d5b0) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002a83d660) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a83d660) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f27ad06490, count: -3
ddb> show registers
rdi 0xffff80002d89e000
rsi 0x27b
rbp 0xffff80002a83d590
rbx 0
rdx 0x1
rcx 0x1
rax 0xfffff1006b81df00
r8 0x180
r9 0xfffff10007ffd958
r10 0xe6b063d19a7ab9d5
r11 0xa6ca34dec54033f4
r12 0xffff80002a738fb8
r13 0xffff8000015eb000
r14 0
r15 0x3
rip 0xffffffff823f68ad sys_shmat+0x39d
cs 0x8
rflags 0x10246 __ALIGN_SIZE+0xf246
rsp 0xffff80002a83d500
ss 0
sys_shmat+0x39d: movq 0(%r14),%rdi
ddb> show proc
PROC (syz-executor) tid=321914 pid=68614 tcnt=5 stat=onproc
flags process=0 proc=4000000<THREAD>
runpri=65, usrpri=65, slppri=32, nice=20
wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
forw=0xffffffffffffffff, list=0xffff80002a739250,0xffffffff83abe518
process=0xffff8000384ca8e0 user=0xffff80002a838000, vmspace=0xfffff1006c4ff468
estcpu=15, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb> ps
PID TID PPID UID S PRLAGS PFLAGS WAIT COMMAND
83569 351673 58420 0 2 0x1006 0 ndp
58420 32507 28059 0 3 0x100002 0x88 sigsusp sh
74414 284383 81809 0 2 0 0 syz-executor
74414 268324 81809 0 3 0 0x4000080 fsleep syz-executor
15303 311449 82251 0 2 0 0 syz-executor
68614 501581 91883 0 2 0 0 syz-executor
68614 369329 91883 0 2 0 0x4000000 syz-executor
68614 319583 91883 0 3 0 0x4000080 fsleep syz-executor
68614 464556 91883 0 2 0 0x4000000 syz-executor
*68614 321914 91883 0 7 0 0x4000000 syz-executor
28059 396628 69462 0 3 0x2 0x80 wait syz-executor
59286 255668 59563 0 3 0x10 0x80 nanoslp syz-executor
59286 448727 59563 0 3 0x10 0x4000080 kqread syz-executor
59286 387978 59563 0 3 0x10 0x4000080 fsleep syz-executor
59286 391023 59563 0 3 0x10 0x4000080 fsleep syz-executor
59286 6816 59563 0 3 0x10 0x4000080 fsleep syz-executor
82251 230997 69462 0 2 0x2 0xc80 syz-executor
20456 293467 69462 0 2 0x2 0 syz-executor
81809 322361 69462 0 3 0x2 0x80 nanoslp syz-executor
24803 416152 69462 0 2 0x2 0 syz-executor
59563 278740 69462 0 2 0x2 0xc80 syz-executor
91883 240441 69462 0 2 0x2 0xc80 syz-executor
71428 373422 69462 0 2 0x2 0 syz-executor
69462 289471 4522 0 3 0x2 0x80 kqread syz-executor
4522 373876 46213 0 3 0x100002 0x88 sigsusp ksh
46213 42495 18893 0 3 0x10 0x88 kqread sshd-session
18893 97087 93815 0 3 0x12 0x80 kqread sshd-session
36952 382652 1 0 3 0x100003 0x80 ttyin getty
93815 66798 1 0 3 0 0x88 kqread sshd
75527 259669 66794 73 3 0x1100010 0x80 kqread syslogd
66794 393787 1 0 3 0x100002 0x80 sbwait syslogd
54636 309507 1 0 3 0x100000 0x80 kqread resolvd
13576 4702 40924 77 3 0x100012 0x80 kqread dhcpleased
11020 499907 40924 77 3 0x100012 0x80 kqread dhcpleased
40924 410622 1 0 3 0 0x80 kqread dhcpleased
39356 372585 0 0 3 0x14000 0x200 bored smr
67083 191968 0 0 2 0x14000 0x200 zerothread
70816 54795 0 0 3 0x14000 0x200 aiodoned aiodoned
89933 246099 0 0 3 0x14000 0x200 syncer update
94303 208905 0 0 3 0x14000 0x200 cleaner cleaner
3222 382447 0 0 3 0x14000 0x200 reaper reaper
37744 19950 0 0 3 0x14000 0x200 pgdaemon pagedaemon
91247 185015 0 0 3 0x14000 0x200 bored viomb
3074 306280 0 0 3 0x14000 0x40000200 acpi0 acpi0
38939 393873 0 0 3 0x14000 0x200 bored softnet0
81665 165464 0 0 3 0x14000 0x200 smrbar systqmp
2639 39030 0 0 3 0x14000 0x200 bored systq
21984 448307 0 0 2 0x14000 0x40000200 softclock
45433 130499 0 0 3 0x14000 0x40000200 idle0
1 469927 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 11038 12168K 12184K 166960K 12214 0
pcb 18 14K 16K 166960K 108 0
rtable 236 6K 7K 166960K 476 0
pf 32 13K 15K 166960K 44 0
ifaddr 44 7K 7K 166960K 63 0
ifgroup 50 2K 2K 166960K 68 0
sysctl 3 1K 9K 166960K 8 0
counters 33 17K 17K 166960K 38 0
ioctlops 0 0K 4K 166960K 50 0
iov 0 0K 16K 166960K 6 0
mount 1 1K 1K 166960K 1 0
log 0 0K 0K 166960K 4 0
vnodes 1297 82K 82K 166960K 1503 0
UFS quota 1 32K 32K 166960K 1 0
UFS mount 5 36K 36K 166960K 5 0
shm 3 5K 5K 166960K 4 0
VM map 2 1K 1K 166960K 2 0
sem 5 0K 0K 166960K 6 0
dirhash 12 2K 2K 166960K 12 0
ACPI 1692 195K 286K 166960K 12470 0
file desc 16 57K 97K 166960K 297 0
sigio 0 0K 0K 166960K 1 0
proc 59 59K 124K 166960K 629 0
subproc 72 4K 4K 166960K 108 0
NFS srvsock 1 0K 0K 166960K 1 0
NFS daemon 1 16K 16K 166960K 1 0
ip_moptions 0 0K 0K 166960K 5 0
in_multi 99 6K 6K 166960K 146 0
ether_multi 1 0K 0K 166960K 2 0
mrt 0 0K 0K 166960K 10 0
ISOFS mount 1 32K 32K 166960K 1 0
MSDOSFS mount 1 16K 16K 166960K 1 0
ttys 67 307K 307K 166960K 67 0
exec 1 0K 1K 166960K 440 0
fusefs mount 1 32K 32K 166960K 1 0
pfkey data 0 0K 0K 166960K 1 0
tdb 3 0K 0K 166960K 3 0
VM swap 8 62K 64K 166960K 10 0
UVM amap 200 151K 159K 166960K 4245 0
UVM aobj 6 3K 3K 166960K 7 0
pinsyscall 36 72K 96K 166960K 1508 0
memdesc 1 4K 4K 166960K 1 0
crypto data 1 1K 1K 166960K 1 0
ip6_options 0 0K 0K 166960K 4 0
NDP 13 0K 2K 166960K 40 0
temp 41 9107K 9171K 166960K 4818 0
kqueue 15 24K 26K 166960K 51 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 56 0 53 1 0 1 1 0 8 0
rtentry 136 155 0 46 4 0 4 4 0 8 0
unpcb 144 63 0 46 1 0 1 1 0 8 0
syncache 336 5 0 5 2 1 1 1 0 8 1
tcpcb 736 33 0 29 1 0 1 1 0 8 0
arp 96 26 0 8 1 0 1 1 0 8 0
inpcb 328 211 0 202 7 0 7 7 0 8 5
nd6 112 36 0 13 1 0 1 1 0 8 0
pkpcb 40 1 0 1 1 0 1 1 0 8 1
kcovpl 48 12 0 4 1 0 1 1 0 8 0
ppxss 1072 1 0 1 1 0 1 1 0 8 1
pfstscr 40 2 0 2 1 0 1 1 0 8 1
pfrktable 1344 1 0 1 1 1 0 1 0 8 0
pftag 88 1 0 0 1 0 1 1 0 8 0
pfstkey 128 2 0 2 1 0 1 1 0 8 1
pfstate 384 1 0 1 1 0 1 1 0 8 1
pfrule 1360 4 0 3 2 1 1 1 0 8 0
art_heap8 4096 1 0 0 1 0 1 1 0 8 0
art_heap4 256 643 0 190 33 3 30 30 0 8 1
art_table 40 644 0 190 5 0 5 5 0 8 0
art_node 32 155 0 55 1 0 1 1 0 8 0
sysvmsgpl 40 10 0 8 1 0 1 1 0 8 0
semapl 72 3 0 0 1 0 1 1 0 8 0
shmpl 120 4 0 1 1 0 1 1 0 8 0
dirhash 1024 17 0 0 3 0 3 3 0 8 0
dino2pl 256 1770 0 302 92 0 92 92 0 8 0
ffsino 256 1770 0 302 92 0 92 92 0 8 0
nchpl 144 2118 0 413 64 0 64 64 0 8 0
vnodes 216 1929 0 0 108 0 108 108 0 8 0
namei 1024 7697 0 7692 4 2 2 3 0 8 1
kstatmem 264 33 0 10 2 0 2 2 0 8 0
scsiplug 72 2 0 2 2 1 1 1 0 8 1
scxspl 216 6790 0 6790 3 2 1 3 1 8 1
plimitpl 152 50 0 34 1 0 1 1 0 8 0
sigapl 424 587 0 546 7 1 6 6 0 8 0
knotepl 120 7619 0 7567 11 1 10 10 0 8 8
kqueuepl 184 56 0 45 1 0 1 1 0 8 0
pipepl 304 144 0 117 3 0 3 3 0 8 0
fdescpl 448 574 0 546 5 1 4 5 0 8 0
filepl 120 2407 0 2200 9 0 9 9 0 8 2
lockfpl 104 46 0 44 1 0 1 1 0 8 0
lockfspl 48 21 0 19 1 0 1 1 0 8 0
sessionpl 144 32 0 24 1 0 1 1 0 8 0
pgrppl 48 44 0 28 1 0 1 1 0 8 0
ucredpl 104 327 0 315 1 0 1 1 0 8 0
zombiepl 144 611 0 611 2 1 1 1 0 8 1
processpl 1160 587 0 546 4 0 4 4 0 8 0
procpl 664 775 0 725 6 0 6 6 0 8 1
sockpl 552 333 0 304 7 0 7 7 0 8 4
mcl64k 65536 3 0 3 2 1 1 1 0 8 1
mcl16k 16384 2 0 2 1 0 1 1 0 8 1
mcl12k 12288 1 0 1 1 0 1 1 0 8 1
mcl9k128 9344 1 0 1 1 1 0 1 0 8 0
mcl8k 8192 6 0 6 2 1 1 1 0 8 1
mcl4k 4096 2651 0 2596 13 4 9 13 0 8 1
mcl2k 2048 274 0 272 3 0 3 3 0 8 2
mextrefs 64 127 0 126 1 0 1 1 0 8 0
mtagpl 96 4 0 4 1 1 0 1 0 8 0
mbufpl 256 5669 0 5494 15 1 14 14 0 8 1
bufpl 272 2410 0 102 154 0 154 154 0 8 0
anonpl 24 105834 0 102889 27 6 21 27 0 187 0
amapchunkpl 152 16348 0 15940 30 3 27 27 0 158 9
amappl16 200 1822 0 1806 6 4 2 5 0 8 0
amappl15 192 23 0 23 1 1 0 1 0 8 0
amappl14 184 463 0 461 1 0 1 1 0 8 0
amappl13 176 126 0 116 1 0 1 1 0 8 0
amappl12 168 835 0 810 2 0 2 2 0 8 0
amappl11 160 4 0 4 1 1 0 1 0 8 0
amappl10 152 58 0 48 1 0 1 1 0 8 0
amappl9 144 268 0 268 1 1 0 1 0 8 0
amappl8 136 110 0 109 1 0 1 1 0 8 0
amappl7 128 149 0 138 1 0 1 1 0 8 0
amappl6 120 192 0 190 1 0 1 1 0 8 0
amappl5 112 95 0 87 1 0 1 1 0 8 0
amappl4 104 275 0 260 1 0 1 1 0 8 0
amappl3 96 2123 0 2045 3 0 3 3 0 8 0
amappl2 88 682 0 614 2 0 2 2 0 8 0
amappl1 80 11131 0 10588 13 0 13 13 0 8 1
amappl 88 3471 0 3333 5 0 5 5 0 92 0
uvmvnodes 80 101 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 128 254 0 254 2 1 1 1 0 8 1
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 6 0 1 1 0 1 1 0 8 0
uaddrrnd 24 574 0 546 1 0 1 1 0 8 0
uaddrbest 32 2 0 0 1 0 1 1 0 8 0
uaddr 24 574 0 546 1 0 1 1 0 8 0
vmmpekpl 168 6548 0 6497 3 0 3 3 0 8 0
vmmpepl 168 45892 0 44246 82 0 82 82 0 357 5
vmsppl 368 573 0 546 4 1 3 4 0 8 0
rwobjpl 40 16269 0 15335 11 0 11 11 0 8 0
pdppl 4096 1154 0 1092 106 38 68 82 0 8 6
pvpl 32 265801 0 258218 99 21 78 93 0 265 3
pmappl 216 573 0 546 3 0 3 3 0 8 0
extentpl 40 45 0 27 1 0 1 1 0 8 0
phpool 112 538 0 56 15 0 15 15 0 8 0
ddb> machine ddbcpu 0
No such command
ddb> trace
sys_shmat(ffff80002a738fb8,ffff80002a83d660,ffff80002a83d5b0) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002a83d660) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a83d660) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f27ad06490, count: -3
ddb> machine ddbcpu 1
No such command
ddb> trace
sys_shmat(ffff80002a738fb8,ffff80002a83d660,ffff80002a83d5b0) at sys_shmat+0x39d sys/kern/sysv_shm.c:283
syscall(ffff80002a83d660) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a83d660) at syscall+0x962 sys/arch/amd64/amd64/trap.c:791
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f27ad06490, count: -3
Struck through repros no longer work on HEAD.