* Re: [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid
2025-07-28 20:55 [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
@ 2025-07-28 23:37 ` syzbot
2025-07-29 7:22 ` syztest Arnaud Lecomte
` (2 more replies)
2025-09-04 10:17 ` syztest Arnaud Lecomte
2025-09-04 14:11 ` syztest Arnaud Lecomte
2 siblings, 3 replies; 18+ messages in thread
From: syzbot @ 2025-07-28 23:37 UTC (permalink / raw)
To: andrii, ast, bpf, daniel, eddyz87, haoluo, john.fastabend, jolsa,
kpsingh, linux-kernel, martin.lau, netdev, sdf, song,
syzkaller-bugs, yonghong.song
syzbot has found a reproducer for the following issue on:
HEAD commit: 5b4c54ac49af bpf: Fix various typos in verifier.c comments
git tree: bpf-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17441782580000
kernel config: https://syzkaller.appspot.com/x/.config?x=934611ae034ab218
dashboard link: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16f294a2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14349034580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5a5cfac28d08/disk-5b4c54ac.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bb5b9f9f1b33/vmlinux-5b4c54ac.xz
kernel image: https://storage.googleapis.com/syzbot-assets/14b928da2760/bzImage-5b4c54ac.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: slab-out-of-bounds in __bpf_get_stackid+0x677/0xcf0 kernel/bpf/stackmap.c:265
Write of size 8 at addr ffff8880439aa258 by task syz-executor265/6114
CPU: 1 UID: 0 PID: 6114 Comm: syz-executor265 Not tainted 6.16.0-rc6-syzkaller-g5b4c54ac49af #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/0x230 mm/kasan/report.c:480
kasan_report+0x118/0x150 mm/kasan/report.c:593
__bpf_get_stackid+0x677/0xcf0 kernel/bpf/stackmap.c:265
____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:1322 [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+0x284/0x4b0 kernel/trace/bpf_trace.c:2298
__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:4829
slab_free_after_rcu_debug+0x60/0x2a0 mm/slub.c:4680
rcu_do_batch kernel/rcu/tree.c:2576 [inline]
rcu_core+0xca8/0x1710 kernel/rcu/tree.c:2832
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:xas_load+0xd9/0x5b0 lib/xarray.c:244
Code: 42 0f b6 04 28 84 c0 0f 85 3a 04 00 00 49 8d 5e fe 48 8b 44 24 08 0f b6 28 48 89 d8 48 c1 e8 03 48 89 44 24 20 42 0f b6 04 28 <84> c0 0f 85 34 04 00 00 44 0f b6 23 44 0f b6 fd 44 89 ff 44 89 e6
RSP: 0000:ffffc9000459f898 EFLAGS: 00000a02
RAX: 0000000000000000 RBX: ffff888025438840 RCX: ffff88807c050000
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000002
RBP: 0000000000000000 R08: ffff88807c050000 R09: 0000000000000002
R10: 0000000000000003 R11: 0000000000000000 R12: ffffc9000459fb32
R13: dffffc0000000000 R14: ffff888025438842 R15: 0000000000000002
xas_find+0x157/0x990 lib/xarray.c:1406
next_uptodate_folio+0x32/0x5d0 mm/filemap.c:3562
filemap_map_pages+0x21f/0x1740 mm/filemap.c:3714
do_fault_around mm/memory.c:5548 [inline]
do_read_fault mm/memory.c:5581 [inline]
do_fault mm/memory.c:5724 [inline]
do_pte_missing mm/memory.c:4251 [inline]
handle_pte_fault mm/memory.c:6069 [inline]
__handle_mm_fault+0x3687/0x5620 mm/memory.c:6212
handle_mm_fault+0x40a/0x8e0 mm/memory.c:6381
do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f3d52e29438
Code: Unable to access opcode bytes at 0x7f3d52e2940e.
RSP: 002b:00007fff46c399c8 EFLAGS: 00010206
RAX: 00007f3d52e59ad8 RBX: 0000000000000000 RCX: 0000000000000004
RDX: 00007f3d52e5ad00 RSI: 0000000000000000 RDI: 00007f3d52e59ad8
RBP: 00007f3d52e58118 R08: 00007fff46c39a3c R09: 00007fff46c39a3c
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3d52e5ace8
R13: 0000000000000000 R14: 00007f3d52e5ad00 R15: 00007f3d52db0290
</TASK>
Allocated by task 6114:
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:377 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4328 [inline]
__kmalloc_node_noprof+0x276/0x4e0 mm/slub.c:4334
kmalloc_node_noprof include/linux/slab.h:932 [inline]
__bpf_map_area_alloc kernel/bpf/syscall.c:391 [inline]
bpf_map_area_alloc+0x64/0x180 kernel/bpf/syscall.c:404
prealloc_elems_and_freelist+0x86/0x1d0 kernel/bpf/stackmap.c:51
stack_map_alloc+0x33f/0x4c0 kernel/bpf/stackmap.c:114
map_create+0xaa0/0x1310 kernel/bpf/syscall.c:1477
__sys_bpf+0x60f/0x870 kernel/bpf/syscall.c:6004
__do_sys_bpf kernel/bpf/syscall.c:6132 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6130 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6130
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 ffff8880439aa000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 24 bytes to the right of
allocated 576-byte region [ffff8880439aa000, ffff8880439aa240)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x439a8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a441dc0 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a441dc0 0000000000000000 dead000000000001
head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea00010e6a01 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 5514, tgid 5514 (dhcpcd), ts 48384102667, free_ts 48383277611
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
prep_new_page mm/page_alloc.c:1712 [inline]
get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3669
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
alloc_slab_page mm/slub.c:2451 [inline]
allocate_slab+0x8a/0x3b0 mm/slub.c:2619
new_slab mm/slub.c:2673 [inline]
___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
__slab_alloc mm/slub.c:3949 [inline]
__slab_alloc_node mm/slub.c:4024 [inline]
slab_alloc_node mm/slub.c:4185 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x305/0x4f0 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
load_elf_phdrs fs/binfmt_elf.c:525 [inline]
load_elf_binary+0x2cd/0x2790 fs/binfmt_elf.c:854
search_binary_handler fs/exec.c:1670 [inline]
exec_binprm fs/exec.c:1702 [inline]
bprm_execve+0x999/0x1450 fs/exec.c:1754
do_execveat_common+0x510/0x6a0 fs/exec.c:1860
do_execve fs/exec.c:1934 [inline]
__do_sys_execve fs/exec.c:2010 [inline]
__se_sys_execve fs/exec.c:2005 [inline]
__x64_sys_execve+0x94/0xb0 fs/exec.c:2005
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 5514 tgid 5514 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1248 [inline]
__free_frozen_pages+0xc71/0xe70 mm/page_alloc.c:2706
discard_slab mm/slub.c:2717 [inline]
__put_partials+0x161/0x1c0 mm/slub.c:3186
put_cpu_partial+0x17c/0x250 mm/slub.c:3261
__slab_free+0x2f7/0x400 mm/slub.c:4513
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:329
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4148 [inline]
slab_alloc_node mm/slub.c:4197 [inline]
__do_kmalloc_node mm/slub.c:4327 [inline]
__kmalloc_noprof+0x224/0x4f0 mm/slub.c:4340
kmalloc_noprof include/linux/slab.h:909 [inline]
tomoyo_add_entry security/tomoyo/common.c:2132 [inline]
tomoyo_supervisor+0xbd5/0x1480 security/tomoyo/common.c:2204
tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
tomoyo_env_perm+0x149/0x1e0 security/tomoyo/environ.c:63
tomoyo_environ security/tomoyo/domain.c:672 [inline]
tomoyo_find_next_domain+0x15cf/0x1aa0 security/tomoyo/domain.c:888
tomoyo_bprm_check_security+0x11c/0x180 security/tomoyo/tomoyo.c:102
security_bprm_check+0x89/0x270 security/security.c:1302
search_binary_handler fs/exec.c:1660 [inline]
exec_binprm fs/exec.c:1702 [inline]
bprm_execve+0x8ee/0x1450 fs/exec.c:1754
do_execveat_common+0x510/0x6a0 fs/exec.c:1860
do_execve fs/exec.c:1934 [inline]
__do_sys_execve fs/exec.c:2010 [inline]
__se_sys_execve fs/exec.c:2005 [inline]
__x64_sys_execve+0x94/0xb0 fs/exec.c:2005
Memory state around the buggy address:
ffff8880439aa100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880439aa180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880439aa200: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff8880439aa280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880439aa300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax
5: 84 c0 test %al,%al
7: 0f 85 3a 04 00 00 jne 0x447
d: 49 8d 5e fe lea -0x2(%r14),%rbx
11: 48 8b 44 24 08 mov 0x8(%rsp),%rax
16: 0f b6 28 movzbl (%rax),%ebp
19: 48 89 d8 mov %rbx,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 89 44 24 20 mov %rax,0x20(%rsp)
25: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax
* 2a: 84 c0 test %al,%al <-- trapping instruction
2c: 0f 85 34 04 00 00 jne 0x466
32: 44 0f b6 23 movzbl (%rbx),%r12d
36: 44 0f b6 fd movzbl %bpl,%r15d
3a: 44 89 ff mov %r15d,%edi
3d: 44 89 e6 mov %r12d,%esi
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
^ permalink raw reply [flat|nested] 18+ messages in thread* syztest
2025-07-28 23:37 ` syzbot
@ 2025-07-29 7:22 ` Arnaud Lecomte
2025-07-29 8:56 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-10-12 13:04 ` Syz Test Arnaud lecomte
2025-10-12 13:56 ` test Arnaud lecomte
2 siblings, 1 reply; 18+ messages in thread
From: Arnaud Lecomte @ 2025-07-29 7:22 UTC (permalink / raw)
To: syzbot+c9b724fbb41cf2538b7b; +Cc: bpf, linux-kernel, netdev, syzkaller-bugs
#syz test
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -230,7 +230,7 @@ static long __bpf_get_stackid(struct bpf_map *map,
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
- u32 hash, id, trace_nr, trace_len, i;
+ u32 hash, id, trace_nr, trace_len, i, max_depth;
bool user = flags & BPF_F_USER_STACK;
u64 *ips;
bool hash_matches;
@@ -241,6 +241,19 @@ static long __bpf_get_stackid(struct bpf_map *map,
trace_nr = trace->nr - skip;
trace_len = trace_nr * sizeof(u64);
+
+ /* Clamp the trace to max allowed depth */
+ if (stack_map_use_build_id(map))
+ max_depth = smap->map.value_size / sizeof(struct bpf_stack_build_id);
+ else
+ max_depth = smap->map.value_size / sizeof(u64);
+
+ if (trace_nr > max_depth)
+ trace_nr = max_depth;
+
+ ips = trace->ip + skip;
+
+
ips = trace->ip + skip;
hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
id = hash & (smap->n_buckets - 1);
--
^ permalink raw reply [flat|nested] 18+ messages in thread
* Syz Test
2025-07-28 23:37 ` syzbot
2025-07-29 7:22 ` syztest Arnaud Lecomte
@ 2025-10-12 13:04 ` Arnaud lecomte
2025-10-12 13:29 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-10-12 13:56 ` test Arnaud lecomte
2 siblings, 1 reply; 18+ messages in thread
From: Arnaud lecomte @ 2025-10-12 13:04 UTC (permalink / raw)
To: syzbot+c9b724fbb41cf2538b7b; +Cc: bpf, linux-kernel, netdev, syzkaller-bugs
#syz test
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..c0ee51db8eed 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -42,6 +42,28 @@ static inline int stack_map_data_size(struct bpf_map *map)
sizeof(struct bpf_stack_build_id) : sizeof(u64);
}
+/**
+ * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth
+ * @size: Size of the buffer/map value in bytes
+ * @elem_size: Size of each stack trace element
+ * @flags: BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...)
+ *
+ * Return: Maximum number of stack trace entries that can be safely stored
+ */
+static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags)
+{
+ u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 max_depth;
+ u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack);
+
+ max_depth = size / elem_size;
+ max_depth += skip;
+ if (max_depth > curr_sysctl_max_stack)
+ return curr_sysctl_max_stack;
+
+ return max_depth;
+}
+
static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
u64 elem_size = sizeof(struct stack_map_bucket) +
@@ -251,8 +273,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
+ u32 hash, id, trace_nr, trace_len, i, max_depth;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
- u32 hash, id, trace_nr, trace_len, i;
bool user = flags & BPF_F_USER_STACK;
u64 *ips;
bool hash_matches;
@@ -261,7 +283,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
/* skipping more than usable stack trace */
return -EFAULT;
- trace_nr = trace->nr - skip;
+ max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags);
+ trace_nr = min_t(u32, trace->nr - skip, max_depth - skip);
trace_len = trace_nr * sizeof(u64);
ips = trace->ip + skip;
hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
@@ -300,20 +323,17 @@ static long __bpf_get_stackid(struct bpf_map *map,
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
- u32 max_depth = map->value_size / stack_map_data_size(map);
- u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 elem_size = stack_map_data_size(map);
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
+ u32 max_depth;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
- max_depth += skip;
- if (max_depth > sysctl_perf_event_max_stack)
- max_depth = sysctl_perf_event_max_stack;
-
+ max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
false, false);
@@ -390,15 +410,11 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
nr_kernel = count_kernel_ip(trace);
+ __u64 nr = trace->nr; /* save original */
if (kernel) {
- __u64 nr = trace->nr;
-
trace->nr = nr_kernel;
ret = __bpf_get_stackid(map, trace, flags);
-
- /* restore nr */
- trace->nr = nr;
} else { /* user */
u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -409,6 +425,10 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
ret = __bpf_get_stackid(map, trace, flags);
}
+
+ /* restore nr */
+ trace->nr = nr;
+
return ret;
}
@@ -426,7 +446,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags, bool may_fault)
{
- u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
+ u32 trace_nr, copy_len, elem_size, max_depth;
bool user_build_id = flags & BPF_F_USER_BUILD_ID;
bool crosstask = task && task != current;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -458,21 +478,20 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
goto clear;
}
- num_elem = size / elem_size;
- max_depth = num_elem + skip;
- if (sysctl_perf_event_max_stack < max_depth)
- max_depth = sysctl_perf_event_max_stack;
+ max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
if (may_fault)
rcu_read_lock(); /* need RCU for perf's callchain below */
- if (trace_in)
+ if (trace_in) {
trace = trace_in;
- else if (kernel && task)
+ trace->nr = min_t(u32, trace->nr, max_depth);
+ } else if (kernel && task) {
trace = get_callchain_entry_for_task(task, max_depth);
- else
+ } else {
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
crosstask, false);
+ }
if (unlikely(!trace) || trace->nr < skip) {
if (may_fault)
@@ -481,7 +500,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
}
trace_nr = trace->nr - skip;
- trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
copy_len = trace_nr * elem_size;
ips = trace->ip + skip;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* test
2025-07-28 23:37 ` syzbot
2025-07-29 7:22 ` syztest Arnaud Lecomte
2025-10-12 13:04 ` Syz Test Arnaud lecomte
@ 2025-10-12 13:56 ` Arnaud lecomte
2025-10-12 14:22 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2 siblings, 1 reply; 18+ messages in thread
From: Arnaud lecomte @ 2025-10-12 13:56 UTC (permalink / raw)
To: syzbot+c9b724fbb41cf2538b7b
Cc: bpf, linux-kernel, netdev, syzkaller-bugs, contact
#syz test
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..c0ee51db8eed 100644
--- a/kernel/bpf/stackmap.c
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
- u32 max_depth = map->value_size / stack_map_data_size(map);
- u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 elem_size = stack_map_data_size(map);
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
+ u32 max_depth;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
- max_depth += skip;
- if (max_depth > sysctl_perf_event_max_stack)
- max_depth = sysctl_perf_event_max_stack;
-
+ max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
false, false);
@@ -371,15 +391,11 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
nr_kernel = count_kernel_ip(trace);
+ __u64 nr = trace->nr; /* save original */
if (kernel) {
- __u64 nr = trace->nr;
-
trace->nr = nr_kernel;
ret = __bpf_get_stackid(map, trace, flags);
-
- /* restore nr */
- trace->nr = nr;
} else { /* user */
u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -390,6 +406,10 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
ret = __bpf_get_stackid(map, trace, flags);
}
+
+ /* restore nr */
+ trace->nr = nr;
+
return ret;
}
@@ -406,7 +426,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags, bool may_fault)
{
- u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
+ u32 trace_nr, copy_len, elem_size, max_depth;
bool user_build_id = flags & BPF_F_USER_BUILD_ID;
bool crosstask = task && task != current;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -438,21 +458,20 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
goto clear;
}
- num_elem = size / elem_size;
- max_depth = num_elem + skip;
- if (sysctl_perf_event_max_stack < max_depth)
- max_depth = sysctl_perf_event_max_stack;
+ max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
if (may_fault)
rcu_read_lock(); /* need RCU for perf's callchain below */
- if (trace_in)
+ if (trace_in) {
trace = trace_in;
- else if (kernel && task)
+ trace->nr = min_t(u32, trace->nr, max_depth);
+ } else if (kernel && task) {
trace = get_callchain_entry_for_task(task, max_depth);
- else
+ } else {
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
crosstask, false);
+ }
if (unlikely(!trace) || trace->nr < skip) {
if (may_fault)
@@ -461,7 +480,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
}
trace_nr = trace->nr - skip;
- trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
copy_len = trace_nr * elem_size;
ips = trace->ip + skip;
--
2.47.3
^ permalink raw reply [flat|nested] 18+ messages in thread
* syztest
2025-07-28 20:55 [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-07-28 23:37 ` syzbot
@ 2025-09-04 10:17 ` Arnaud Lecomte
2025-09-04 11:54 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-09-04 14:11 ` syztest Arnaud Lecomte
2 siblings, 1 reply; 18+ messages in thread
From: Arnaud Lecomte @ 2025-09-04 10:17 UTC (permalink / raw)
To: syzbot+c9b724fbb41cf2538b7b; +Cc: bpf, linux-kernel, netdev, syzkaller-bugs
#syz test
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..29e05c9ff1bd 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -42,6 +42,28 @@ static inline int stack_map_data_size(struct bpf_map *map)
sizeof(struct bpf_stack_build_id) : sizeof(u64);
}
+/**
+ * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth
+ * @size: Size of the buffer/map value in bytes
+ * @elem_size: Size of each stack trace element
+ * @flags: BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...)
+ *
+ * Return: Maximum number of stack trace entries that can be safely stored
+ */
+static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags)
+{
+ u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 max_depth;
+ u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack);
+
+ max_depth = size / elem_size;
+ max_depth += skip;
+ if (max_depth > curr_sysctl_max_stack)
+ return curr_sysctl_max_stack;
+
+ return max_depth;
+}
+
static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
u64 elem_size = sizeof(struct stack_map_bucket) +
@@ -300,20 +322,17 @@ static long __bpf_get_stackid(struct bpf_map *map,
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
- u32 max_depth = map->value_size / stack_map_data_size(map);
- u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 elem_size = stack_map_data_size(map);
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
+ u32 max_depth;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
- max_depth += skip;
- if (max_depth > sysctl_perf_event_max_stack)
- max_depth = sysctl_perf_event_max_stack;
-
+ max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
false, false);
@@ -350,6 +369,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
{
struct perf_event *event = ctx->event;
struct perf_callchain_entry *trace;
+ u32 elem_size, max_depth;
bool kernel, user;
__u64 nr_kernel;
int ret;
@@ -371,11 +391,15 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
nr_kernel = count_kernel_ip(trace);
+ elem_size = stack_map_data_size(map);
if (kernel) {
__u64 nr = trace->nr;
trace->nr = nr_kernel;
+ max_depth =
+ stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+ trace->nr = min_t(u32, nr_kernel, max_depth);
ret = __bpf_get_stackid(map, trace, flags);
/* restore nr */
@@ -388,6 +412,9 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
+ max_depth =
+ stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+ trace->nr = min_t(u32, trace->nr, max_depth);
ret = __bpf_get_stackid(map, trace, flags);
}
return ret;
@@ -406,8 +433,8 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags, bool may_fault)
{
- u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
bool user_build_id = flags & BPF_F_USER_BUILD_ID;
+ u32 trace_nr, copy_len, elem_size, max_depth;
bool crosstask = task && task != current;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
bool user = flags & BPF_F_USER_STACK;
@@ -438,21 +465,20 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
goto clear;
}
- num_elem = size / elem_size;
- max_depth = num_elem + skip;
- if (sysctl_perf_event_max_stack < max_depth)
- max_depth = sysctl_perf_event_max_stack;
+ max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
if (may_fault)
rcu_read_lock(); /* need RCU for perf's callchain below */
- if (trace_in)
+ if (trace_in) {
trace = trace_in;
- else if (kernel && task)
+ trace->nr = min_t(u32, trace->nr, max_depth);
+ } else if (kernel && task) {
trace = get_callchain_entry_for_task(task, max_depth);
- else
+ } else {
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
crosstask, false);
+ }
if (unlikely(!trace) || trace->nr < skip) {
if (may_fault)
@@ -461,7 +487,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
}
trace_nr = trace->nr - skip;
- trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
copy_len = trace_nr * elem_size;
ips = trace->ip + skip;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid
2025-09-04 10:17 ` syztest Arnaud Lecomte
@ 2025-09-04 11:54 ` syzbot
0 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2025-09-04 11:54 UTC (permalink / raw)
To: bpf, contact, linux-kernel, netdev, syzkaller-bugs
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
^ permalink raw reply [flat|nested] 18+ messages in thread
* syztest
2025-07-28 20:55 [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-07-28 23:37 ` syzbot
2025-09-04 10:17 ` syztest Arnaud Lecomte
@ 2025-09-04 14:11 ` Arnaud Lecomte
2025-09-04 14:32 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
2025-09-04 14:47 ` syztest Jakub Kicinski
2 siblings, 2 replies; 18+ messages in thread
From: Arnaud Lecomte @ 2025-09-04 14:11 UTC (permalink / raw)
To: syzbot+c9b724fbb41cf2538b7b; +Cc: bpf, linux-kernel, netdev, syzkaller-bugs
#syz test
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..1389712bc1df 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -42,6 +42,28 @@ static inline int stack_map_data_size(struct bpf_map *map)
sizeof(struct bpf_stack_build_id) : sizeof(u64);
}
+/**
+ * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth
+ * @size: Size of the buffer/map value in bytes
+ * @elem_size: Size of each stack trace element
+ * @flags: BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...)
+ *
+ * Return: Maximum number of stack trace entries that can be safely stored
+ */
+static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags)
+{
+ u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 max_depth;
+ u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack);
+
+ max_depth = size / elem_size;
+ max_depth += skip;
+ if (max_depth > curr_sysctl_max_stack)
+ return curr_sysctl_max_stack;
+
+ return max_depth;
+}
+
static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
u64 elem_size = sizeof(struct stack_map_bucket) +
@@ -300,22 +322,20 @@ static long __bpf_get_stackid(struct bpf_map *map,
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags)
{
- u32 max_depth = map->value_size / stack_map_data_size(map);
- u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+ u32 elem_size = stack_map_data_size(map);
bool user = flags & BPF_F_USER_STACK;
struct perf_callchain_entry *trace;
bool kernel = !user;
+ u32 max_depth;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
- max_depth += skip;
- if (max_depth > sysctl_perf_event_max_stack)
- max_depth = sysctl_perf_event_max_stack;
-
+ max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
false, false);
+ trace->nr = min_t(u32, trace->nr, max_depth);
if (unlikely(!trace))
/* couldn't fetch the stack trace */
@@ -350,6 +370,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
{
struct perf_event *event = ctx->event;
struct perf_callchain_entry *trace;
+ u32 elem_size, max_depth;
bool kernel, user;
__u64 nr_kernel;
int ret;
@@ -371,11 +392,15 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
nr_kernel = count_kernel_ip(trace);
+ elem_size = stack_map_data_size(map);
if (kernel) {
__u64 nr = trace->nr;
trace->nr = nr_kernel;
+ max_depth =
+ stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+ trace->nr = min_t(u32, nr_kernel, max_depth);
ret = __bpf_get_stackid(map, trace, flags);
/* restore nr */
@@ -388,6 +413,9 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
return -EFAULT;
flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
+ max_depth =
+ stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+ trace->nr = min_t(u32, trace->nr, max_depth);
ret = __bpf_get_stackid(map, trace, flags);
}
return ret;
@@ -406,8 +434,8 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags, bool may_fault)
{
- u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
bool user_build_id = flags & BPF_F_USER_BUILD_ID;
+ u32 trace_nr, copy_len, elem_size, max_depth;
bool crosstask = task && task != current;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
bool user = flags & BPF_F_USER_STACK;
@@ -438,21 +466,20 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
goto clear;
}
- num_elem = size / elem_size;
- max_depth = num_elem + skip;
- if (sysctl_perf_event_max_stack < max_depth)
- max_depth = sysctl_perf_event_max_stack;
+ max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
if (may_fault)
rcu_read_lock(); /* need RCU for perf's callchain below */
- if (trace_in)
+ if (trace_in) {
trace = trace_in;
- else if (kernel && task)
+ trace->nr = min_t(u32, trace->nr, max_depth);
+ } else if (kernel && task) {
trace = get_callchain_entry_for_task(task, max_depth);
- else
+ } else {
trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
crosstask, false);
+ }
if (unlikely(!trace) || trace->nr < skip) {
if (may_fault)
@@ -461,7 +488,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
}
trace_nr = trace->nr - skip;
- trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
copy_len = trace_nr * elem_size;
ips = trace->ip + skip;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid
2025-09-04 14:11 ` syztest Arnaud Lecomte
@ 2025-09-04 14:32 ` syzbot
2025-09-04 14:47 ` syztest Jakub Kicinski
1 sibling, 0 replies; 18+ messages in thread
From: syzbot @ 2025-09-04 14:32 UTC (permalink / raw)
To: bpf, contact, linux-kernel, netdev, syzkaller-bugs
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 ffff88802fd43258 by task syz.3.65/6980
CPU: 1 UID: 0 PID: 6980 Comm: syz.3.65 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
__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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 4b 87 4b f6 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4f f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 93 2e 14 f6 65 8b 05 6c 71 24 07 85 c0 74 40 48 c7 04 24 0e 36
RSP: 0018:ffffc90003f6fc60 EFLAGS: 00000206
RAX: 237d7f7a06c71d00 RBX: 0000000000000a06 RCX: 237d7f7a06c71d00
RDX: 0000000000000006 RSI: ffffffff8d9b68b0 RDI: 0000000000000001
RBP: ffffc90003f6fcf0 R08: ffffffff8fa37e37 R09: 1ffffffff1f46fc6
R10: dffffc0000000000 R11: fffffbfff1f46fc7 R12: dffffc0000000000
R13: ffff8880641d6a40 R14: ffff888057cc1000 R15: 1ffff920007edf8c
__do_sys_perf_event_open kernel/events/core.c:13712 [inline]
__se_sys_perf_event_open+0x1942/0x1d70 kernel/events/core.c:13353
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: 0033:0x7fd9da58ebe9
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:00007fd9db415038 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007fd9da7b5fa0 RCX: 00007fd9da58ebe9
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 00002000000003c0
RBP: 00007fd9da611e19 R08: 0000000000000003 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd9da7b6038 R14: 00007fd9da7b5fa0 R15: 00007ffee6a22f78
</TASK>
Allocated by task 6980:
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 ffff88802fd43000
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 [ffff88802fd43000, ffff88802fd43240)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2fd40
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88806f32bf01
ksm flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801a44b280 ffffea0001e83e00 dead000000000003
raw: 0000000000000000 0000000080100010 00000000f5000000 ffff88806f32bf01
head: 00fff00000000040 ffff88801a44b280 ffffea0001e83e00 dead000000000003
head: 0000000000000000 0000000080100010 00000000f5000000 ffff88806f32bf01
head: 00fff00000000003 ffffea0000bf5001 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 5882, tgid 5882 (syz-executor), ts 81348212299, free_ts 80466086651
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]
kzalloc_noprof include/linux/slab.h:1039 [inline]
__register_sysctl_table+0x72/0x1340 fs/proc/proc_sysctl.c:1379
neigh_sysctl_register+0x9a2/0xa80 net/core/neighbour.c:3887
devinet_sysctl_register+0xad/0x200 net/ipv4/devinet.c:2715
inetdev_init+0x2b4/0x500 net/ipv4/devinet.c:291
inetdev_event+0x301/0x15b0 net/ipv4/devinet.c:1591
notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
call_netdevice_notifiers net/core/dev.c:2281 [inline]
register_netdevice+0x1608/0x1ae0 net/core/dev.c:11227
__ip_tunnel_create+0x3e7/0x560 net/ipv4/ip_tunnel.c:268
ip_tunnel_init_net+0x2ba/0x800 net/ipv4/ip_tunnel.c:1161
page last free pid 5526 tgid 5526 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_node_noprof+0x1bb/0x3c0 mm/slub.c:4281
__alloc_skb+0x112/0x2d0 net/core/skbuff.c:659
alloc_skb include/linux/skbuff.h:1336 [inline]
alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6665
sock_alloc_send_pskb+0x857/0x990 net/core/sock.c:2980
unix_dgram_sendmsg+0x461/0x1850 net/unix/af_unix.c:2153
sock_sendmsg_nosec net/socket.c:714 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:729
sock_write_iter+0x258/0x330 net/socket.c:1179
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c6/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
Memory state around the buggy address:
ffff88802fd43100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88802fd43180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88802fd43200: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff88802fd43280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802fd43300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 74 05 je 0x7
2: e8 4b 87 4b f6 call 0xf64b8752
7: 48 c7 44 24 20 00 00 movq $0x0,0x20(%rsp)
e: 00 00
10: 9c pushf
11: 8f 44 24 20 pop 0x20(%rsp)
15: f6 44 24 21 02 testb $0x2,0x21(%rsp)
1a: 75 4f jne 0x6b
1c: f7 c3 00 02 00 00 test $0x200,%ebx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 93 2e 14 f6 call 0xf6142ec2 <-- trapping instruction
2f: 65 8b 05 6c 71 24 07 mov %gs:0x724716c(%rip),%eax # 0x72471a2
36: 85 c0 test %eax,%eax
38: 74 40 je 0x7a
3a: 48 rex.W
3b: c7 .byte 0xc7
3c: 04 24 add $0x24,%al
3e: 0e (bad)
3f: 36 ss
Tested on:
commit: 71ca59e2 Merge branch 'fix-bpf_strnstr-len-error'
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=127c3e62580000
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=1381fe62580000
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: syztest
2025-09-04 14:11 ` syztest Arnaud Lecomte
2025-09-04 14:32 ` [syzbot] [bpf?] KASAN: slab-out-of-bounds Write in __bpf_get_stackid syzbot
@ 2025-09-04 14:47 ` Jakub Kicinski
2025-09-04 14:53 ` syztest Lecomte, Arnaud
1 sibling, 1 reply; 18+ messages in thread
From: Jakub Kicinski @ 2025-09-04 14:47 UTC (permalink / raw)
To: Arnaud Lecomte
Cc: syzbot+c9b724fbb41cf2538b7b, bpf, linux-kernel, netdev,
syzkaller-bugs
On Thu, 4 Sep 2025 16:11:13 +0200 Arnaud Lecomte wrote:
> #syz test
You are hereby encouraged to not CC the vger MLs on your attempts
to get your patches tested by syzbot. It's not necessary.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: syztest
2025-09-04 14:47 ` syztest Jakub Kicinski
@ 2025-09-04 14:53 ` Lecomte, Arnaud
0 siblings, 0 replies; 18+ messages in thread
From: Lecomte, Arnaud @ 2025-09-04 14:53 UTC (permalink / raw)
To: Jakub Kicinski
Cc: syzbot+c9b724fbb41cf2538b7b, bpf, linux-kernel, netdev,
syzkaller-bugs
On 04/09/2025 16:47, Jakub Kicinski wrote:
> On Thu, 4 Sep 2025 16:11:13 +0200 Arnaud Lecomte wrote:
>> #syz test
> You are hereby encouraged to not CC the vger MLs on your attempts
> to get your patches tested by syzbot. It's not necessary.
>
Hey, sorry for the inconvenience.
Will be removed.
^ permalink raw reply [flat|nested] 18+ messages in thread
* syztest
2025-03-31 20:23 [syzbot] [rdma?] [s390?] [net?] KASAN: null-ptr-deref Read in smc_tcp_syn_recv_sock syzbot
@ 2025-06-29 13:29 ` Arnaud Lecomte
2025-06-30 6:51 ` syztest Paolo Abeni
2025-06-29 14:47 ` syztest Arnaud Lecomte
2025-06-29 15:10 ` syztest Arnaud Lecomte
2 siblings, 1 reply; 18+ messages in thread
From: Arnaud Lecomte @ 2025-06-29 13:29 UTC (permalink / raw)
To: syzbot+827ae2bfb3a3529333e9
Cc: agordeev, alibuda, davem, edumazet, guwen, horms, jaka, kuba,
linux-kernel, linux-rdma, linux-s390, netdev, pabeni,
syzkaller-bugs, tonylu, wenjia
#syz test
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -123,11 +123,14 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
struct request_sock *req_unhash,
bool *own_req)
{
+ read_lock_bh(&((struct sock *)sk)->sk_callback_lock);
struct smc_sock *smc;
struct sock *child;
-
smc = smc_clcsock_user_data(sk);
+ if (!smc)
+ goto drop;
+
if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
sk->sk_max_ack_backlog)
goto drop;
@@ -148,9 +151,11 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops)
inet_csk(child)->icsk_af_ops = smc->ori_af_ops;
}
+ read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
return child;
drop:
+ read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
dst_release(dst);
tcp_listendrop(sk);
return NULL;
@@ -2613,7 +2618,7 @@ int smc_listen(struct socket *sock, int backlog)
int rc;
smc = smc_sk(sk);
- lock_sock(sk);
+ lock_sock(sock->sk);
rc = -EINVAL;
if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
--
2.43.0
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: syztest
2025-06-29 13:29 ` syztest Arnaud Lecomte
@ 2025-06-30 6:51 ` Paolo Abeni
0 siblings, 0 replies; 18+ messages in thread
From: Paolo Abeni @ 2025-06-30 6:51 UTC (permalink / raw)
To: Arnaud Lecomte, syzbot+827ae2bfb3a3529333e9
Cc: agordeev, alibuda, davem, edumazet, guwen, horms, jaka, kuba,
linux-kernel, linux-rdma, linux-s390, netdev, syzkaller-bugs,
tonylu, wenjia
On 6/29/25 3:29 PM, Arnaud Lecomte wrote:
> #syz test
>
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -123,11 +123,14 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
> struct request_sock *req_unhash,
> bool *own_req)
> {
> + read_lock_bh(&((struct sock *)sk)->sk_callback_lock);
> struct smc_sock *smc;
> struct sock *child;
> -
> smc = smc_clcsock_user_data(sk);
>
> + if (!smc)
> + goto drop;
> +
> if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
> sk->sk_max_ack_backlog)
> goto drop;
> @@ -148,9 +151,11 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
> if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops)
> inet_csk(child)->icsk_af_ops = smc->ori_af_ops;
> }
> + read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
> return child;
>
> drop:
> + read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
> dst_release(dst);
> tcp_listendrop(sk);
> return NULL;
> @@ -2613,7 +2618,7 @@ int smc_listen(struct socket *sock, int backlog)
> int rc;
>
> smc = smc_sk(sk);
> - lock_sock(sk);
> + lock_sock(sock->sk);
>
> rc = -EINVAL;
> if ((sk->sk_state != SMC_INIT && sk->sk_state != SMC_LISTEN) ||
Please stop cc-ing netdev and other kernel ML with this tests. You
should keep just the syzkaller related MLs and a very restricted list of
individuals (i.e. no maintainers).
Thanks,
Paolo
^ permalink raw reply [flat|nested] 18+ messages in thread
* syztest
2025-03-31 20:23 [syzbot] [rdma?] [s390?] [net?] KASAN: null-ptr-deref Read in smc_tcp_syn_recv_sock syzbot
2025-06-29 13:29 ` syztest Arnaud Lecomte
@ 2025-06-29 14:47 ` Arnaud Lecomte
2025-06-29 15:10 ` syztest Arnaud Lecomte
2 siblings, 0 replies; 18+ messages in thread
From: Arnaud Lecomte @ 2025-06-29 14:47 UTC (permalink / raw)
To: syzbot+827ae2bfb3a3529333e9
Cc: agordeev, alibuda, davem, edumazet, guwen, horms, jaka, kuba,
linux-kernel, linux-rdma, linux-s390, netdev, pabeni,
syzkaller-bugs, tonylu, wenjia
#syz test
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -126,8 +126,12 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
struct smc_sock *smc;
struct sock *child;
+ lockdep_assert_held_read(&sk->sk_callback_lock);
smc = smc_clcsock_user_data(sk);
+ if (!smc)
+ goto drop;
+
if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
sk->sk_max_ack_backlog)
goto drop;
--
2.43.0
^ permalink raw reply [flat|nested] 18+ messages in thread
* syztest
2025-03-31 20:23 [syzbot] [rdma?] [s390?] [net?] KASAN: null-ptr-deref Read in smc_tcp_syn_recv_sock syzbot
2025-06-29 13:29 ` syztest Arnaud Lecomte
2025-06-29 14:47 ` syztest Arnaud Lecomte
@ 2025-06-29 15:10 ` Arnaud Lecomte
2 siblings, 0 replies; 18+ messages in thread
From: Arnaud Lecomte @ 2025-06-29 15:10 UTC (permalink / raw)
To: syzbot+827ae2bfb3a3529333e9
Cc: agordeev, alibuda, davem, edumazet, guwen, horms, jaka, kuba,
linux-kernel, linux-rdma, linux-s390, netdev, pabeni,
syzkaller-bugs, tonylu, wenjia
#syz test
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -125,9 +125,12 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
{
struct smc_sock *smc;
struct sock *child;
-
+ read_lock_bh(&((struct sock *)sk)->sk_callback_lock);
smc = smc_clcsock_user_data(sk);
+ if (!smc)
+ goto drop;
+
if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
sk->sk_max_ack_backlog)
goto drop;
@@ -148,9 +151,11 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops)
inet_csk(child)->icsk_af_ops = smc->ori_af_ops;
}
+ read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
return child;
drop:
+ read_unlock_bh(&((struct sock *)sk)->sk_callback_lock);
dst_release(dst);
tcp_listendrop(sk);
return NULL;
--
2.43.0
^ permalink raw reply [flat|nested] 18+ messages in thread