syzbot
KASAN: slab-out-of-bounds Write in stack_map_get_build_id_offset (2)
Status:
upstream: reported C repro on 2026/08/30 23:11
Bug presence:
origin:lts-only
[Documentation on labels]
Reported-by: syzbot+1f96ec84fb9b62c53c87@syzkaller.appspotmail.com
First crash: 26d, last: 2d12h
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Bug presence (2)
| Date |
Name |
Commit |
Repro |
Result |
| 2026/09/12 |
linux-6.1.y (ToT) |
cf82dcca9634 |
C
|
[report] KASAN: slab-out-of-bounds Write in stack_map_get_build_id_offset
|
| 2026/09/12 |
upstream (ToT) |
5225b8eec4c9 |
C
|
Didn't crash |
Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in stack_map_get_build_id_offset+0x849/0x9d0 kernel/bpf/stackmap.c:147
Write of size 4 at addr ffff888078218330 by task syz.0.17/4428
CPU: 1 PID: 4428 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
print_address_description mm/kasan/report.c:316 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:420
kasan_report+0x10b/0x140 mm/kasan/report.c:524
stack_map_get_build_id_offset+0x849/0x9d0 kernel/bpf/stackmap.c:147
__bpf_get_stackid+0x55d/0x920 kernel/bpf/stackmap.c:250
____bpf_get_stackid_pe kernel/bpf/stackmap.c:365 [inline]
bpf_get_stackid_pe+0x33f/0x400 kernel/bpf/stackmap.c:334
bpf_prog_2414a5d5030ea31b+0x21/0x25
bpf_dispatcher_nop_func include/linux/bpf.h:1012 [inline]
__bpf_prog_run include/linux/filter.h:608 [inline]
bpf_prog_run include/linux/filter.h:615 [inline]
bpf_overflow_handler+0x50b/0x790 kernel/events/core.c:10331
__perf_event_overflow+0x457/0x630 kernel/events/core.c:9506
perf_swevent_overflow kernel/events/core.c:9589 [inline]
perf_swevent_event+0x315/0x570 kernel/events/core.c:9640
do_perf_sw_event kernel/events/core.c:9753 [inline]
___perf_sw_event+0x498/0x6d0 kernel/events/core.c:9784
__perf_sw_event+0x135/0x260 kernel/events/core.c:9796
perf_sw_event include/linux/perf_event.h:1254 [inline]
do_user_addr_fault+0x497/0xb20 arch/x86/mm/fault.c:1284
handle_page_fault arch/x86/mm/fault.c:1429 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1482
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:copy_user_enhanced_fast_string+0xa/0x40 arch/x86/lib/copy_user_64.S:166
Code: ff c9 75 f2 89 d1 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 31 c0 0f 01 ca c3 8d 0c ca 89 ca eb 20 0f 01 cb 83 fa 40 72 38 89 d1 <f3> a4 31 c0 0f 01 ca c3 89 ca eb 0a 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900034f7668 EFLAGS: 00050206
RAX: ffffffff84143201 RBX: 0000000000001000 RCX: 0000000000000f80
RDX: 0000000000001000 RSI: 0000200000002000 RDI: ffff88802f4a1080
RBP: 0000000000000000 R08: ffff88802f4a1fff R09: 1ffff11005e943ff
R10: dffffc0000000000 R11: ffffed1005e94400 R12: 00007fffffffe000
R13: 0000000000001ec0 R14: 0000200000001f80 R15: ffff88802f4a1000
copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
raw_copy_from_user arch/x86/include/asm/uaccess_64.h:52 [inline]
copyin+0xe7/0x120 lib/iov_iter.c:183
_copy_from_iter+0x447/0x1130 lib/iov_iter.c:632
copy_page_from_iter+0x77/0x100 lib/iov_iter.c:752
skb_copy_datagram_from_iter+0x2c5/0x6b0 net/core/datagram.c:581
unix_stream_sendmsg+0x4d5/0xa70 net/unix/af_unix.c:2232
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x5ed/0x9a0 net/socket.c:2519
___sys_sendmsg+0x2a2/0x360 net/socket.c:2573
__sys_sendmsg net/socket.c:2602 [inline]
__do_sys_sendmsg net/socket.c:2611 [inline]
__se_sys_sendmsg+0x1c3/0x2b0 net/socket.c:2609
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ffa4779e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd92f63318 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ffa47a25fa0 RCX: 00007ffa4779e159
RDX: 0000000000008841 RSI: 0000200000000500 RDI: 0000000000000006
RBP: 00007ffa4783506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffa47a25fac R14: 00007ffa47a25fa0 R15: 00007ffa47a25fa0
</TASK>
Allocated by task 4428:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slab_common.c:936 [inline]
__kmalloc_node+0xb2/0x240 mm/slab_common.c:943
kmalloc_node include/linux/slab.h:589 [inline]
__bpf_map_area_alloc kernel/bpf/syscall.c:328 [inline]
bpf_map_area_alloc+0x47/0xe0 kernel/bpf/syscall.c:341
prealloc_elems_and_freelist+0x86/0x1c0 kernel/bpf/stackmap.c:51
stack_map_alloc+0x386/0x510 kernel/bpf/stackmap.c:117
find_and_alloc_map kernel/bpf/syscall.c:133 [inline]
map_create+0x524/0xff0 kernel/bpf/syscall.c:1149
__sys_bpf+0x38b/0x780 kernel/bpf/syscall.c:5014
__do_sys_bpf kernel/bpf/syscall.c:5136 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5134 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5134
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff888078218000
which belongs to the cache kmalloc-cg-1k of size 1024
The buggy address is located 816 bytes inside of
1024-byte region [ffff888078218000, ffff888078218400)
The buggy address belongs to the physical page:
page:ffffea0001e08600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78218
head:ffffea0001e08600 order:3 compound_mapcount:0 compound_pincount:0
memcg:ffff888076b6f701
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea000082c000 dead000000000002 ffff88801744c000
raw: 0000000000000000 0000000080100010 00000001ffffffff ffff888076b6f701
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3934, tgid 3934 (dhcpcd), ts 54894160587, free_ts 54651214906
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
prep_new_page mm/page_alloc.c:2567 [inline]
get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
__alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
alloc_slab_page+0x5d/0x180 mm/slub.c:1799
allocate_slab mm/slub.c:1944 [inline]
new_slab+0x87/0x2d0 mm/slub.c:1997
___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
__slab_alloc mm/slub.c:3240 [inline]
slab_alloc_node mm/slub.c:3325 [inline]
__kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
__do_kmalloc_node mm/slab_common.c:935 [inline]
__kmalloc_node_track_caller+0xa0/0x240 mm/slab_common.c:956
kmalloc_reserve net/core/skbuff.c:446 [inline]
__alloc_skb+0x226/0x7d0 net/core/skbuff.c:515
alloc_skb include/linux/skbuff.h:1303 [inline]
alloc_skb_with_frags+0xa7/0x710 net/core/skbuff.c:6188
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2763
unix_dgram_sendmsg+0x5c1/0x16f0 net/unix/af_unix.c:1947
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
sock_write_iter+0x2d5/0x3e0 net/socket.c:1144
do_iter_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x638/0xb10 fs/read_write.c:861
vfs_writev fs/read_write.c:934 [inline]
do_writev+0x27b/0x480 fs/read_write.c:977
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1487 [inline]
free_pcp_prepare mm/page_alloc.c:1537 [inline]
free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
free_slab mm/slub.c:2036 [inline]
discard_slab mm/slub.c:2042 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2591
put_cpu_partial+0x17c/0x250 mm/slub.c:2667
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
slab_alloc_node mm/slub.c:3359 [inline]
__kmem_cache_alloc_node+0x19d/0x270 mm/slub.c:3398
__do_kmalloc_node mm/slab_common.c:935 [inline]
__kmalloc+0xa3/0x240 mm/slab_common.c:949
kmalloc include/linux/slab.h:568 [inline]
tomoyo_realpath_from_path+0xe2/0x5c0 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x26f/0x610 security/tomoyo/file.c:822
security_inode_getattr+0xcf/0x120 security/security.c:1365
vfs_getattr+0x26/0x3a0 fs/stat.c:158
vfs_fstat fs/stat.c:183 [inline]
__do_sys_newfstat fs/stat.c:447 [inline]
__se_sys_newfstat fs/stat.c:444 [inline]
__x64_sys_newfstat+0x13d/0x220 fs/stat.c:444
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
Memory state around the buggy address:
ffff888078218200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888078218280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888078218300: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
^
ffff888078218380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888078218400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: ff c9 dec %ecx
2: 75 f2 jne 0xfffffff6
4: 89 d1 mov %edx,%ecx
6: c1 e9 03 shr $0x3,%ecx
9: 83 e2 07 and $0x7,%edx
c: f3 48 a5 rep movsq %ds:(%rsi),%es:(%rdi)
f: 89 d1 mov %edx,%ecx
11: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi)
13: 31 c0 xor %eax,%eax
15: 0f 01 ca clac
18: c3 ret
19: 8d 0c ca lea (%rdx,%rcx,8),%ecx
1c: 89 ca mov %ecx,%edx
1e: eb 20 jmp 0x40
20: 0f 01 cb stac
23: 83 fa 40 cmp $0x40,%edx
26: 72 38 jb 0x60
28: 89 d1 mov %edx,%ecx
* 2a: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction
2c: 31 c0 xor %eax,%eax
2e: 0f 01 ca clac
31: c3 ret
32: 89 ca mov %ecx,%edx
34: eb 0a jmp 0x40
36: 90 nop
37: 90 nop
38: 90 nop
39: 90 nop
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
Struck through repros no longer work on HEAD.