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: 19d, last: 23h52m
▶
▼
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+0x99e/0x9d0 kernel/bpf/stackmap.c:147
Write of size 4 at addr ffff88802750fb30 by task syz.0.18/4431
CPU: 1 PID: 4431 Comm: syz.0.18 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+0x99e/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_short_string+0xd/0x40 arch/x86/lib/copy_user_64.S:233
Code: 74 0a 89 d1 f3 a4 89 c8 0f 01 ca c3 89 d0 0f 01 ca c3 01 ca eb e7 90 90 90 90 90 90 90 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a
RSP: 0018:ffffc900034a72a8 EFLAGS: 00050202
RAX: ffffffff84164701 RBX: 000000000000000b RCX: 0000000000000001
RDX: 0000000000000003 RSI: ffff88807d59066c RDI: 000020000000cf3d
RBP: 0000000000000000 R08: 40203023636e7566 R09: 1ffff1100fab20ce
R10: dffffc0000000000 R11: ffffed100fab20cf R12: 00007fffffffeff5
R13: 000000000000000b R14: 000020000000cf3d R15: ffff88807d59066c
copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
_copy_to_user+0xea/0x130 lib/usercopy.c:41
copy_to_user include/linux/uaccess.h:169 [inline]
bpf_verifier_vlog+0x172/0x3a0 kernel/bpf/log.c:34
verbose+0x1f0/0x2b0 kernel/bpf/verifier.c:303
add_subprog_and_kfunc kernel/bpf/verifier.c:2165 [inline]
bpf_check+0x2f56/0x11010 kernel/bpf/verifier.c:15583
bpf_prog_load+0x100e/0x1530 kernel/bpf/syscall.c:2651
__sys_bpf+0x5b8/0x780 kernel/bpf/syscall.c:5032
__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
RIP: 0033:0x7f24e0b9e159
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:00007fffa70f3068 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f24e0e25fa0 RCX: 00007f24e0b9e159
RDX: 0000000000000048 RSI: 000020000000e000 RDI: 0000000000000005
RBP: 00007f24e0c3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f24e0e25fac R14: 00007f24e0e25fa0 R15: 00007f24e0e25fa0
</TASK>
Allocated by task 4431:
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 ffff88802750f800
which belongs to the cache kmalloc-cg-1k of size 1024
The buggy address is located 816 bytes inside of
1024-byte region [ffff88802750f800, ffff88802750fc00)
The buggy address belongs to the physical page:
page:ffffea00009d4200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27508
head:ffffea00009d4200 order:3 compound_mapcount:0 compound_pincount:0
memcg:ffff88803038ea01
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff88801744c000
raw: 0000000000000000 0000000080100010 00000001ffffffff ffff88803038ea01
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 3933, tgid 3933 (dhcpcd), ts 68351079376, free_ts 68349952520
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_large_kmalloc+0xfd/0x1a0 mm/slab_common.c:913
skb_free_head net/core/skbuff.c:762 [inline]
skb_release_data+0x5e9/0x7e0 net/core/skbuff.c:791
skb_release_all net/core/skbuff.c:856 [inline]
__kfree_skb net/core/skbuff.c:870 [inline]
consume_skb+0xa2/0x100 net/core/skbuff.c:1038
netlink_recvmsg+0x5e3/0xe00 net/netlink/af_netlink.c:1955
____sys_recvmsg+0x2c8/0x5b0 net/socket.c:-1
___sys_recvmsg+0x210/0x590 net/socket.c:2780
__sys_recvmsg net/socket.c:2810 [inline]
__do_sys_recvmsg net/socket.c:2820 [inline]
__se_sys_recvmsg net/socket.c:2817 [inline]
__x64_sys_recvmsg+0x20d/0x2e0 net/socket.c:2817
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
Memory state around the buggy address:
ffff88802750fa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88802750fa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88802750fb00: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
^
ffff88802750fb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802750fc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 74 0a je 0xc
2: 89 d1 mov %edx,%ecx
4: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi)
6: 89 c8 mov %ecx,%eax
8: 0f 01 ca clac
b: c3 ret
c: 89 d0 mov %edx,%eax
e: 0f 01 ca clac
11: c3 ret
12: 01 ca add %ecx,%edx
14: eb e7 jmp 0xfffffffd
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: 90 nop
1c: 90 nop
1d: 89 d1 mov %edx,%ecx
1f: 83 e2 07 and $0x7,%edx
22: c1 e9 03 shr $0x3,%ecx
25: 74 12 je 0x39
27: 4c 8b 06 mov (%rsi),%r8
* 2a: 4c 89 07 mov %r8,(%rdi) <-- trapping instruction
2d: 48 8d 76 08 lea 0x8(%rsi),%rsi
31: 48 8d 7f 08 lea 0x8(%rdi),%rdi
35: ff c9 dec %ecx
37: 75 ee jne 0x27
39: 21 d2 and %edx,%edx
3b: 74 10 je 0x4d
3d: 89 d1 mov %edx,%ecx
3f: 8a .byte 0x8a
Struck through repros no longer work on HEAD.