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Message-ID: <68b97dda.050a0220.192772.0005.GAE@google.com>
Date: Thu, 04 Sep 2025 04:54:02 -0700
From: syzbot <syzbot+c9b724fbb41cf2538b7b@...kaller.appspotmail.com>
To: bpf@...r.kernel.org, contact@...aud-lcm.com, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-out-of-bounds Write in __bpf_get_stackid
==================================================================
BUG: KASAN: slab-out-of-bounds in __bpf_get_stackid+0x677/0xcf0 kernel/bpf/stackmap.c:287
Write of size 8 at addr ffff88807a2d9258 by task syz.1.290/7428
CPU: 1 UID: 0 PID: 7428 Comm: syz.1.290 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<IRQ>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xca/0x240 mm/kasan/report.c:482
kasan_report+0x118/0x150 mm/kasan/report.c:595
__bpf_get_stackid+0x677/0xcf0 kernel/bpf/stackmap.c:287
____bpf_get_stackid_raw_tp kernel/trace/bpf_trace.c:1810 [inline]
bpf_get_stackid_raw_tp+0x196/0x210 kernel/trace/bpf_trace.c:1799
bpf_prog_b724608cae728045+0x27/0x2f
bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline]
__bpf_prog_run include/linux/filter.h:718 [inline]
bpf_prog_run include/linux/filter.h:725 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline]
bpf_trace_run2+0x281/0x4b0 kernel/trace/bpf_trace.c:2298
__traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:94
__do_trace_kfree include/trace/events/kmem.h:94 [inline]
trace_kfree include/trace/events/kmem.h:94 [inline]
kfree+0x3a0/0x440 mm/slub.c:4866
slab_free_after_rcu_debug+0x60/0x2a0 mm/slub.c:4717
rcu_do_batch kernel/rcu/tree.c:2605 [inline]
rcu_core+0xcab/0x1770 kernel/rcu/tree.c:2861
handle_softirqs+0x283/0x870 kernel/softirq.c:579
__do_softirq kernel/softirq.c:613 [inline]
invoke_softirq kernel/softirq.c:453 [inline]
__irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:rcu_is_watching_curr_cpu include/linux/context_tracking.h:128 [inline]
RIP: 0010:rcu_is_watching+0x3a/0xb0 kernel/rcu/tree.c:751
Code: e8 eb f2 d2 09 89 c3 83 f8 08 73 65 49 bf 00 00 00 00 00 fc ff df 4c 8d 34 dd 10 ed bd 8d 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 <74> 08 4c 89 f7 e8 dc b8 7c 00 48 c7 c3 98 6f a1 92 49 03 1e 48 89
RSP: 0018:ffffc9000b4d7ad8 EFLAGS: 00000246
RAX: 1ffffffff1b7bda3 RBX: 0000000000000001 RCX: 0f1baf102ea8c100
RDX: 0000000000000000 RSI: ffffffff8be33260 RDI: ffffffff8be33220
RBP: ffffffff81b2dcc0 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc9000b4d7c40 R11: fffff5200169af8b R12: 0000000000000002
R13: ffffffff8e139ea0 R14: ffffffff8dbded18 R15: dffffc0000000000
trace_lock_acquire include/trace/events/lock.h:24 [inline]
lock_acquire+0x5f/0x360 kernel/locking/lockdep.c:5831
rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
rcu_read_lock include/linux/rcupdate.h:841 [inline]
class_rcu_constructor include/linux/rcupdate.h:1155 [inline]
futex_hash+0x5d/0x2d0 kernel/futex/core.c:308
class_hb_constructor kernel/futex/futex.h:240 [inline]
futex_wake+0x161/0x560 kernel/futex/waitwake.c:172
do_futex+0x395/0x420 kernel/futex/syscalls.c:107
__do_sys_futex kernel/futex/syscalls.c:179 [inline]
__se_sys_futex+0x36f/0x400 kernel/futex/syscalls.c:160
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132bf8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f132cd870e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f132c1b5fa8 RCX: 00007f132bf8ebe9
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f132c1b5fac
RBP: 00007f132c1b5fa0 R08: 7fffffffffffffff R09: 0000000000000000
R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f132c1b6038 R14: 00007ffd03290180 R15: 00007ffd03290268
</TASK>
Allocated by task 7428:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:405
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4365 [inline]
__kmalloc_node_noprof+0x276/0x4e0 mm/slub.c:4371
kmalloc_node_noprof include/linux/slab.h:932 [inline]
__bpf_map_area_alloc kernel/bpf/syscall.c:393 [inline]
bpf_map_area_alloc+0x64/0x180 kernel/bpf/syscall.c:406
prealloc_elems_and_freelist+0x86/0x1d0 kernel/bpf/stackmap.c:73
stack_map_alloc+0x33f/0x4c0 kernel/bpf/stackmap.c:136
map_create+0xaa3/0x14d0 kernel/bpf/syscall.c:1480
__sys_bpf+0x60f/0x870 kernel/bpf/syscall.c:6011
__do_sys_bpf kernel/bpf/syscall.c:6139 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6137 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6137
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88807a2d9000
which belongs to the cache kmalloc-cg-1k of size 1024
The buggy address is located 24 bytes to the right of
allocated 576-byte region [ffff88807a2d9000, ffff88807a2d9240)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7a2d8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888054d19001
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a44b280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080100010 00000000f5000000 ffff888054d19001
head: 00fff00000000040 ffff88801a44b280 dead000000000100 dead000000000122
head: 0000000000000000 0000000080100010 00000000f5000000 ffff888054d19001
head: 00fff00000000003 ffffea0001e8b601 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 5237, tgid 5237 (udevd), ts 36597748986, free_ts 36397116210
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:2487 [inline]
allocate_slab+0x8a/0x370 mm/slub.c:2655
new_slab mm/slub.c:2709 [inline]
___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
__slab_alloc mm/slub.c:3981 [inline]
__slab_alloc_node mm/slub.c:4056 [inline]
slab_alloc_node mm/slub.c:4217 [inline]
__do_kmalloc_node mm/slub.c:4364 [inline]
__kmalloc_noprof+0x305/0x4f0 mm/slub.c:4377
kmalloc_noprof include/linux/slab.h:909 [inline]
kmalloc_array_noprof include/linux/slab.h:948 [inline]
alloc_pipe_info+0x1fd/0x4d0 fs/pipe.c:815
get_pipe_inode fs/pipe.c:894 [inline]
create_pipe_files+0x8a/0x7e0 fs/pipe.c:926
__do_pipe_flags+0x46/0x1f0 fs/pipe.c:988
do_pipe2+0x9c/0x170 fs/pipe.c:1036
__do_sys_pipe2 fs/pipe.c:1054 [inline]
__se_sys_pipe2 fs/pipe.c:1052 [inline]
__x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1052
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5244 tgid 5244 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2895
discard_slab mm/slub.c:2753 [inline]
__put_partials+0x156/0x1a0 mm/slub.c:3218
put_cpu_partial+0x17c/0x250 mm/slub.c:3293
__slab_free+0x2d5/0x3c0 mm/slub.c:4550
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:340
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4180 [inline]
slab_alloc_node mm/slub.c:4229 [inline]
kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4236
getname_flags+0xb8/0x540 fs/namei.c:146
do_readlinkat+0xbc/0x500 fs/stat.c:575
__do_sys_readlink fs/stat.c:613 [inline]
__se_sys_readlink fs/stat.c:610 [inline]
__x64_sys_readlink+0x7f/0x90 fs/stat.c:610
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff88807a2d9100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807a2d9180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807a2d9200: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff88807a2d9280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88807a2d9300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: e8 eb f2 d2 09 call 0x9d2f2f0
5: 89 c3 mov %eax,%ebx
7: 83 f8 08 cmp $0x8,%eax
a: 73 65 jae 0x71
c: 49 bf 00 00 00 00 00 movabs $0xdffffc0000000000,%r15
13: fc ff df
16: 4c 8d 34 dd 10 ed bd lea -0x724212f0(,%rbx,8),%r14
1d: 8d
1e: 4c 89 f0 mov %r14,%rax
21: 48 c1 e8 03 shr $0x3,%rax
25: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
* 2a: 74 08 je 0x34 <-- trapping instruction
2c: 4c 89 f7 mov %r14,%rdi
2f: e8 dc b8 7c 00 call 0x7cb910
34: 48 c7 c3 98 6f a1 92 mov $0xffffffff92a16f98,%rbx
3b: 49 03 1e add (%r14),%rbx
3e: 48 rex.W
3f: 89 .byte 0x89
Tested on:
commit: 71ca59e2 Merge branch 'fix-bpf_strnstr-len-error'
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=143c1162580000
kernel config: https://syzkaller.appspot.com/x/.config?x=807fffde4ddbe9ec
dashboard link: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=158e0134580000
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