[syzbot] [bpf?] possible deadlock in __stack_map_get

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f99c5f563c17 Merge tag 'nf-24-03-21' of git://git.kernel.o..
git tree: net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d7c52b180000
kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=dddd99ae26c656485d89
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10869857180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f1f7cb180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/65d3f3eb786e/disk-f99c5f56.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/799cf7f28ff8/vmlinux-f99c5f56.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ab26c60c3845/bzImage-f99c5f56.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dddd99...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
6.8.0-syzkaller-05271-gf99c5f563c17 #0 Not tainted
--------------------------------------------
syz-executor224/5098 is trying to acquire lock:
ffff888021ef61d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x14b/0x4b0 kernel/bpf/queue_stack_maps.c:140

but task is already holding lock:
ffff888021ef51d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x14b/0x4b0 kernel/bpf/queue_stack_maps.c:140

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&qs->lock);
lock(&qs->lock);

*** DEADLOCK ***

May be due to missing lock nesting notation

4 locks held by syz-executor224/5098:
#0: ffffffff8e200c68 (pcpu_alloc_mutex){+.+.}-{3:3}, at: pcpu_alloc+0x27b/0x1670 mm/percpu.c:1769
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420
#2: ffff888021ef51d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x14b/0x4b0 kernel/bpf/queue_stack_maps.c:140
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420

stack backtrace:
CPU: 0 PID: 5098 Comm: syz-executor224 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
check_deadlock kernel/locking/lockdep.c:3062 [inline]
validate_chain+0x15c1/0x58e0 kernel/locking/lockdep.c:3856
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__stack_map_get+0x14b/0x4b0 kernel/bpf/queue_stack_maps.c:140
bpf_prog_7a16b54e5ee857f9+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
__traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
trace_contention_end+0xf6/0x120 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x939/0xc60 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162
__stack_map_get+0x14b/0x4b0 kernel/bpf/queue_stack_maps.c:140
bpf_prog_7a16b54e5ee857f9+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
__traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
pcpu_alloc+0x27b/0x1670 mm/percpu.c:1769
bpf_prog_alloc_no_stats+0x10b/0x4a0 kernel/bpf/core.c:112
bpf_prog_alloc+0x3b/0x1b0 kernel/bpf/core.c:144
bpf_prog_load+0x7f7/0x20f0 kernel/bpf/syscall.c:2805
__sys_bpf+0x4ee/0x810 kernel/bpf/syscall.c:5631
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7fb8f4667f69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc6855faf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb8f4667f69
RDX: 0000000000000090 RSI: 00000000200000c0 RDI: 0000000000000005
RBP: 0000000000000000 R08: 00000000000000a0 R09: 00000000000000a0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>


---
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If you want to undo deduplication, reply with:
#syz undup

[Hillf Danton]

On Thu, 18 Apr 2024 13:00:28 -0700

> syzbot found the following issue on:
>
> HEAD commit: f99c5f563c17 Merge tag 'nf-24-03-21' of git://git.kernel.o..
> git tree: net

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f1f7cb180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git f99c5f563c17

--- x/kernel/bpf/queue_stack_maps.c
+++ y/kernel/bpf/queue_stack_maps.c
@@ -124,7 +124,7 @@ out:
return err;
}

-
+static DEFINE_PER_CPU(int, map_depth);
static long __stack_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
@@ -132,12 +132,22 @@ static long __stack_map_get(struct bpf_m
int err = 0;
void *ptr;
u32 index;
+ int dumy;
+ int *depth = &dumy;

if (in_nmi()) {
if (!raw_spin_trylock_irqsave(&qs->lock, flags))
return -EBUSY;
} else {
+ preempt_disable_notrace();
+ depth = this_cpu_ptr(&map_depth);
+ if (*depth) {
+ preempt_enable_notrace();
+ return -EDEADLK;
+ }
raw_spin_lock_irqsave(&qs->lock, flags);
+ *depth += 1;
+ preempt_enable_notrace();
}

if (queue_stack_map_is_empty(qs)) {
@@ -157,6 +167,7 @@ static long __stack_map_get(struct bpf_m
qs->head = index;

out:
+ *depth -= 1;
raw_spin_unlock_irqrestore(&qs->lock, flags);
return err;
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __stack_map_get

============================================
WARNING: possible recursive locking detected

6.8.0-syzkaller-05271-gf99c5f563c17-dirty #0 Not tainted
--------------------------------------------
syz-executor.3/6102 is trying to acquire lock:
ffff88806da7b1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

but task is already holding lock:

ffff88807eace1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&qs->lock);
lock(&qs->lock);

*** DEADLOCK ***

May be due to missing lock nesting notation

4 locks held by syz-executor.3/6102:
#0: ffffffff8e17cf88 (tracepoints_mutex){+.+.}-{3:3}, at: tracepoint_probe_unregister+0x32/0x990 kernel/tracepoint.c:548

#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420

#2: ffff88807eace1d8 (&qs->lock){-.-.}-{2:2}, at: __stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#3: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420

stack backtrace:

CPU: 0 PID: 6102 Comm: syz-executor.3 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
check_deadlock kernel/locking/lockdep.c:3062 [inline]
validate_chain+0x15c1/0x58e0 kernel/locking/lockdep.c:3856
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162

__stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

bpf_prog_7a16b54e5ee857f9+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
__traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
trace_contention_end+0xf6/0x120 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x939/0xc60 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162

__stack_map_get+0x286/0x6f0 kernel/bpf/queue_stack_maps.c:148

bpf_prog_7a16b54e5ee857f9+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
__traceiter_contention_end+0x7b/0xb0 include/trace/events/lock.h:122
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752

tracepoint_probe_unregister+0x32/0x990 kernel/tracepoint.c:548
bpf_raw_tp_link_release+0x63/0x90 kernel/bpf/syscall.c:3482
bpf_link_free kernel/bpf/syscall.c:3033 [inline]
bpf_link_put_direct+0x123/0x1b0 kernel/bpf/syscall.c:3064
bpf_link_release+0x3b/0x50 kernel/bpf/syscall.c:3071
__fput+0x429/0x8a0 fs/file_table.c:423
__do_sys_close fs/open.c:1557 [inline]
__se_sys_close fs/open.c:1542 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1542
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f7e74c7cd5a
Code: 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c 24 0c e8 03 7f 02 00 8b 7c 24 0c 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 63 7f 02 00 8b 44 24
RSP: 002b:00007ffc624e2df0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f7e74c7cd5a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000226 R08: 0000001b2f460000 R09: 00007f7e74dabf8c
R10: 00007ffc624e2f40 R11: 0000000000000293 R12: 00007f7e74801260
R13: ffffffffffffffff R14: 00007f7e74800000 R15: 0000000000019ae9
</TASK>


Tested on:

commit: f99c5f56 Merge tag 'nf-24-03-21' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
console output: https://syzkaller.appspot.com/x/log.txt?x=124f9ae7180000

kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=dddd99ae26c656485d89
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=10257bb3180000

[Hillf Danton]

On Thu, 18 Apr 2024 13:00:28 -0700

> syzbot found the following issue on:
>
> HEAD commit: f99c5f563c17 Merge tag 'nf-24-03-21' of git://git.kernel.o..
> git tree: net

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f1f7cb180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git f99c5f563c17

--- x/kernel/bpf/queue_stack_maps.c
+++ y/kernel/bpf/queue_stack_maps.c
@@ -124,7 +124,7 @@ out:
return err;
}

-
+static DEFINE_PER_CPU(int, map_depth);
static long __stack_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);

@@ -132,12 +132,18 @@ static long __stack_map_get(struct bpf_m

int err = 0;
void *ptr;
u32 index;
+ int dumy;
+ int *depth = &dumy;

if (in_nmi()) {
if (!raw_spin_trylock_irqsave(&qs->lock, flags))
return -EBUSY;
} else {

- raw_spin_lock_irqsave(&qs->lock, flags);

+ preempt_disable_notrace();
+ depth = this_cpu_ptr(&map_depth);

+ *depth += 1;
+ raw_spin_lock_irqsave_nested(&qs->lock, flags, *depth);
+ preempt_enable_notrace();
}

if (queue_stack_map_is_empty(qs)) {
@@ -157,6 +163,7 @@ static long __stack_map_get(struct bpf_m

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+dddd99...@syzkaller.appspotmail.com

Tested on:

commit: f99c5f56 Merge tag 'nf-24-03-21' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git

console output: https://syzkaller.appspot.com/x/log.txt?x=1710ae6f180000

kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=dddd99ae26c656485d89
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=105a7ec3180000

Note: testing is done by a robot and is best-effort only.