syzbot
KASAN: slab-out-of-bounds Write in stack_map_get_build_id_offset
Status:
upstream: reported C repro on 2026/08/30 23:23
Reported-by: syzbot+891bd26fad4b84a456b8@syzkaller.appspotmail.com
First crash: 19d, last: 23h05m
Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in stack_map_get_build_id_offset+0x6c0/0x720 kernel/bpf/stackmap.c:144
Write of size 4 at addr ffff88807cf81330 by task syz.0.17/5929
CPU: 1 PID: 5929 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+0x18c/0x250 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xa8/0x210 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
stack_map_get_build_id_offset+0x6c0/0x720 kernel/bpf/stackmap.c:144
__bpf_get_stackid+0x564/0x900 kernel/bpf/stackmap.c:247
____bpf_get_stackid_pe kernel/bpf/stackmap.c:362 [inline]
bpf_get_stackid_pe+0x343/0x410 kernel/bpf/stackmap.c:331
bpf_prog_2414a5d5030ea31b+0x29/0x2d
bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
__bpf_prog_run include/linux/filter.h:617 [inline]
bpf_prog_run include/linux/filter.h:624 [inline]
bpf_overflow_handler+0x1fc/0x510 kernel/events/core.c:10584
__perf_event_overflow+0x461/0x660 kernel/events/core.c:9720
perf_swevent_overflow kernel/events/core.c:9803 [inline]
perf_swevent_event+0x319/0x570 kernel/events/core.c:9854
do_perf_sw_event kernel/events/core.c:9967 [inline]
___perf_sw_event+0x4ab/0x730 kernel/events/core.c:9998
__perf_sw_event+0x139/0x270 kernel/events/core.c:10010
perf_sw_event include/linux/perf_event.h:1442 [inline]
do_user_addr_fault+0x1242/0x12d0 arch/x86/mm/fault.c:1278
handle_page_fault arch/x86/mm/fault.c:1463 [inline]
exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:rep_movs_alternative+0x33/0x90 arch/x86/lib/copy_user_64.S:58
Code: 40 83 f9 08 73 21 85 c9 74 0f 8a 06 88 07 48 ff c7 48 ff c6 48 ff c9 75 f1 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 8b 06 <48> 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 df 83 f9 08 73 e8 eb
RSP: 0018:ffffc90003d2f310 EFLAGS: 00050206
RAX: 40203023636e7566 RBX: 000000000000000b RCX: 000000000000000b
RDX: 0000000000000000 RSI: ffff888077e8868c RDI: 000020000000cf3d
RBP: ffff888077e88668 R08: ffff888077e88696 R09: 1ffff1100efd10d2
R10: dffffc0000000000 R11: ffffed100efd10d3 R12: 000020000000cf48
R13: 000000000000000b R14: 000020000000cf3d R15: ffff888077e8868c
copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
raw_copy_to_user arch/x86/include/asm/uaccess_64.h:133 [inline]
_copy_to_user+0x85/0xa0 lib/usercopy.c:41
copy_to_user include/linux/uaccess.h:191 [inline]
bpf_verifier_vlog+0x2f1/0x840 kernel/bpf/log.c:124
verbose+0x11e/0x1a0 kernel/bpf/verifier.c:370
add_subprog_and_kfunc kernel/bpf/verifier.c:3092 [inline]
bpf_check+0x305c/0xec40 kernel/bpf/verifier.c:20615
bpf_prog_load+0x10fa/0x1610 kernel/bpf/syscall.c:2753
__sys_bpf+0x5ba/0x890 kernel/bpf/syscall.c:5491
__do_sys_bpf kernel/bpf/syscall.c:5595 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5593 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5593
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa87839e159
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:00007fff6b177318 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fa878625fa0 RCX: 00007fa87839e159
RDX: 0000000000000048 RSI: 000020000000e000 RDI: 0000000000000005
RBP: 00007fa87843506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa878625fac R14: 00007fa878625fa0 R15: 00007fa878625fa0
</TASK>
Allocated by task 5929:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:198 [inline]
__do_kmalloc_node mm/slab_common.c:1007 [inline]
__kmalloc_node+0xb6/0x240 mm/slab_common.c:1014
kmalloc_node include/linux/slab.h:620 [inline]
__bpf_map_area_alloc kernel/bpf/syscall.c:303 [inline]
bpf_map_area_alloc+0x5e/0x110 kernel/bpf/syscall.c:316
prealloc_elems_and_freelist+0x86/0x1c0 kernel/bpf/stackmap.c:51
stack_map_alloc+0x32b/0x4b0 kernel/bpf/stackmap.c:114
map_create+0x877/0x12f0 kernel/bpf/syscall.c:1247
__sys_bpf+0x651/0x890 kernel/bpf/syscall.c:5473
__do_sys_bpf kernel/bpf/syscall.c:5595 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5593 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5593
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
The buggy address belongs to the object at ffff88807cf81000
which belongs to the cache kmalloc-cg-1k of size 1024
The buggy address is located 0 bytes to the right of
allocated 816-byte region [ffff88807cf81000, ffff88807cf81330)
The buggy address belongs to the physical page:
page:ffffea0001f3e000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7cf80
head:ffffea0001f3e000 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888072b64501
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c4f280 0000000000000000 0000000000000001
raw: 0000000000000000 0000000080100010 00000001ffffffff ffff888072b64501
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 5715, tgid 5715 (dhcpcd-run-hook), ts 71315224706, free_ts 71283920414
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
prep_new_page mm/page_alloc.c:1589 [inline]
get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
__alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
alloc_slab_page+0x5d/0x180 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2d0 mm/slub.c:2081
___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
__kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0xa7/0x240 mm/slab_common.c:1020
kmalloc_array include/linux/slab.h:637 [inline]
kcalloc include/linux/slab.h:668 [inline]
alloc_pipe_info+0x1f9/0x4b0 fs/pipe.c:813
get_pipe_inode fs/pipe.c:887 [inline]
create_pipe_files+0x87/0x700 fs/pipe.c:919
__do_pipe_flags+0x4c/0x2c0 fs/pipe.c:968
do_pipe2+0xab/0x190 fs/pipe.c:1019
__do_sys_pipe2 fs/pipe.c:1037 [inline]
__se_sys_pipe2 fs/pipe.c:1035 [inline]
__x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1035
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1182 [inline]
free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
discard_slab mm/slub.c:2127 [inline]
__unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
put_cpu_partial+0x17c/0x250 mm/slub.c:2743
__slab_free+0x319/0x400 mm/slub.c:3700
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6a/0x4d0 mm/slab.h:770
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x17e/0x2c0 mm/slub.c:3519
vm_area_alloc+0x24/0x1d0 kernel/fork.c:487
__mmap_region mm/mmap.c:2770 [inline]
mmap_region+0xcfa/0x2090 mm/mmap.c:2941
do_mmap+0x98f/0x10a0 mm/mmap.c:1385
vm_mmap_pgoff+0x1c4/0x3f0 mm/util.c:556
ksys_mmap_pgoff+0x4c9/0x720 mm/mmap.c:1431
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
Memory state around the buggy address:
ffff88807cf81200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807cf81280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807cf81300: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
^
ffff88807cf81380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807cf81400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 40 83 f9 08 rex cmp $0x8,%ecx
4: 73 21 jae 0x27
6: 85 c9 test %ecx,%ecx
8: 74 0f je 0x19
a: 8a 06 mov (%rsi),%al
c: 88 07 mov %al,(%rdi)
e: 48 ff c7 inc %rdi
11: 48 ff c6 inc %rsi
14: 48 ff c9 dec %rcx
17: 75 f1 jne 0xa
19: c3 ret
1a: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
21: 00 00 00
24: 0f 1f 00 nopl (%rax)
27: 48 8b 06 mov (%rsi),%rax
* 2a: 48 89 07 mov %rax,(%rdi) <-- trapping instruction
2d: 48 83 c6 08 add $0x8,%rsi
31: 48 83 c7 08 add $0x8,%rdi
35: 83 e9 08 sub $0x8,%ecx
38: 74 df je 0x19
3a: 83 f9 08 cmp $0x8,%ecx
3d: 73 e8 jae 0x27
3f: eb .byte 0xeb
Struck through repros no longer work on HEAD.