[syzbot] [bpf?] [net?] BUG: sleeping function called from invalid context in sock_map_delete_elem

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8d245acc1e88 Merge tag 'char-misc-6.17-rc3' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11513062580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1e1566c7726877e
dashboard link: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
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=109d7062580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=126bea34580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/096739d8f0ec/disk-8d245acc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/83a21aa9b978/vmlinux-8d245acc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7e7f165a3b29/bzImage-8d245acc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6107, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 1
3 locks held by syz.0.17/6107:
#0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: bpf_test_timer_enter+0x1a/0x140 net/bpf/test_run.c:40
#1: ffffffff8d84a760 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0xa1/0x400 kernel/softirq.c:163
#2: ffff888032e15a98 (&stab->lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock_rt.h:88 [inline]
#2: ffff888032e15a98 (&stab->lock){+...}-{3:3}, at: __sock_map_delete net/core/sock_map.c:421 [inline]
#2: ffff888032e15a98 (&stab->lock){+...}-{3:3}, at: sock_map_delete_elem+0xb7/0x170 net/core/sock_map.c:452
Preemption disabled at:
[<ffffffff891fce58>] bpf_test_timer_enter+0xf8/0x140 net/bpf/test_run.c:42
CPU: 0 UID: 0 PID: 6107 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
__might_resched+0x44b/0x5d0 kernel/sched/core.c:8957
__rt_spin_lock kernel/locking/spinlock_rt.c:48 [inline]
rt_spin_lock+0xc7/0x2c0 kernel/locking/spinlock_rt.c:57
spin_lock_bh include/linux/spinlock_rt.h:88 [inline]
__sock_map_delete net/core/sock_map.c:421 [inline]
sock_map_delete_elem+0xb7/0x170 net/core/sock_map.c:452
bpf_prog_2c29ac5cdc6b1842+0x43/0x4b
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_prog_run_pin_on_cpu include/linux/filter.h:742 [inline]
bpf_flow_dissect+0x132/0x400 net/core/flow_dissector.c:1024
bpf_prog_test_run_flow_dissector+0x37c/0x5c0 net/bpf/test_run.c:1416
bpf_prog_test_run+0x2ca/0x340 kernel/bpf/syscall.c:4590
__sys_bpf+0x581/0x870 kernel/bpf/syscall.c:6047
__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
RIP: 0033:0x7f637004ebe9
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:00007fffc4e2e8a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f6370275fa0 RCX: 00007f637004ebe9
RDX: 0000000000000050 RSI: 0000200000000180 RDI: 000000000000000a
RBP: 00007f63700d1e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6370275fa0 R14: 00007f6370275fa0 R15: 0000000000000003
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
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If you attach or paste a git patch, syzbot will apply it before testing.

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#syz undup

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Re: [syzbot] [bpf?] [net?] BUG: sleeping function called from invalid context in sock_map_delete_elem
Author: chandna.l...@gmail.com

#syz test
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1368,7 +1368,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };
+ struct bpf_test_timer t = { NO_MIGRATE };
u32 size = kattr->test.data_size_in;
struct bpf_flow_dissector ctx = {};
u32 repeat = kattr->test.repeat;
--

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Re: [bpf?] [net?] BUG: sleeping function called from invalid context in sock_map_delete_elem
Author: lis...@listout.xyz

#syz test

--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c

@@ -38,10 +38,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
__acquires(rcu)
{
rcu_read_lock();
- if (t->mode == NO_PREEMPT)
- preempt_disable();
- else
- migrate_disable();
+ migrate_disable();

t->time_start = ktime_get_ns();
}
@@ -51,10 +48,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
{
t->time_start = 0;

- if (t->mode == NO_PREEMPT)
- preempt_enable();
- else
- migrate_enable();
+ migrate_enable();
rcu_read_unlock();
}


--
Regards,
listout

[Brahmajit Das]

#syz test

The syzkaller report exposed a BUG: “sleeping function called from
invalid context” in sock_map_delete_elem, which happens when
`bpf_test_timer_enter()` disables preemption but the delete path later
invokes a sleeping function while still in that context. Specifically:

- The crash trace shows `bpf_test_timer_enter()` acquiring a
preempt_disable path (via t->mode == NO_PREEMPT), but the symmetric
release path always calls migrate_enable(), mismatching the earlier
disable.
- As a result, preemption remains disabled across the
sock_map_delete_elem path, leading to a sleeping call under an invalid
context. :contentReference[oaicite:0]{index=0}

To fix this, normalize the disable/enable pairing: always use
migrate_disable()/migrate_enable() regardless of t->mode. This ensures
that we never remain with preemption disabled unintentionally when
entering the delete path, and avoids invalid-context sleeping.

Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com
Signed-off-by: Brahmajit Das <lis...@listout.xyz>
---
net/bpf/test_run.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfb03ee0bb62..07ffe7d92c1c 100644

--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -38,10 +38,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
__acquires(rcu)
{
rcu_read_lock();
- if (t->mode == NO_PREEMPT)
- preempt_disable();
- else
- migrate_disable();
+ migrate_disable();

t->time_start = ktime_get_ns();
}
@@ -51,10 +48,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
{
t->time_start = 0;

- if (t->mode == NO_PREEMPT)
- preempt_enable();
- else
- migrate_enable();
+ migrate_enable();
rcu_read_unlock();
}

--

2.51.0

[Alexei Starovoitov]

pls search previous thread on this subject.

pw-bot: cr

[syzbot]

Hello,

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

Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com
Tested-by: syzbot+1f1fbe...@syzkaller.appspotmail.com

Tested on:

commit: 5472d60c Merge tag 'trace-v6.18-2' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159b91e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2b842a78bbee09b1
dashboard link: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
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=11f50dcd980000

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

[Brahmajit Das]

#syz test

The syzkaller report exposed a BUG: “sleeping function called from
invalid context” in sock_map_delete_elem, which happens when
`bpf_test_timer_enter()` disables preemption but the delete path later
invokes a sleeping function while still in that context. Specifically:

- The crash trace shows `bpf_test_timer_enter()` acquiring a
preempt_disable path (via t->mode == NO_PREEMPT), but the symmetric
release path always calls migrate_enable(), mismatching the earlier
disable.
- As a result, preemption remains disabled across the
sock_map_delete_elem path, leading to a sleeping call under an invalid
context. :contentReference[oaicite:0]{index=0}

To fix this, normalize the disable/enable pairing: always use
migrate_disable()/migrate_enable() regardless of t->mode. This ensures
that we never remain with preemption disabled unintentionally when
entering the delete path, and avoids invalid-context sleeping.

Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com
Signed-off-by: Brahmajit Das <lis...@listout.xyz>
---

net/bpf/test_run.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfb03ee0bb62..92ff05821003 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2017 Facebook
*/
+#include "linux/rcupdate.h"
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
@@ -29,7 +30,6 @@
#include <trace/events/bpf_test_run.h>

struct bpf_test_timer {
- enum { NO_PREEMPT, NO_MIGRATE } mode;
u32 i;
u64 time_start, time_spent;
};
@@ -38,10 +38,8 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)

__acquires(rcu)
{
rcu_read_lock();
- if (t->mode == NO_PREEMPT)
- preempt_disable();
- else
- migrate_disable();

+ /*migrate_disable();*/
+ rcu_read_lock_dont_migrate();

t->time_start = ktime_get_ns();
}
@@ -51,10 +49,8 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
{
t->time_start = 0;

- if (t->mode == NO_PREEMPT)

- preempt_enable();
- else
- migrate_enable();

+ /*migrate_enable();*/
+ rcu_read_unlock_migrate();
rcu_read_unlock();
}

@@ -374,7 +370,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,

{
struct xdp_test_data xdp = { .batch_size = batch_size };
- struct bpf_test_timer t = { .mode = NO_MIGRATE };
+ struct bpf_test_timer t = {};
int ret;

if (!repeat)
@@ -404,7 +400,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
struct bpf_prog_array_item item = {.prog = prog};
struct bpf_run_ctx *old_ctx;
struct bpf_cg_run_ctx run_ctx;
- struct bpf_test_timer t = { NO_MIGRATE };
+ struct bpf_test_timer t = {};
enum bpf_cgroup_storage_type stype;
int ret;

@@ -1377,7 +1373,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,

const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };

+ struct bpf_test_timer t = {};

u32 size = kattr->test.data_size_in;
struct bpf_flow_dissector ctx = {};
u32 repeat = kattr->test.repeat;

@@ -1445,7 +1441,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,

union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };

+ struct bpf_test_timer t = {};
struct bpf_prog_array *progs = NULL;
struct bpf_sk_lookup_kern ctx = {};

u32 repeat = kattr->test.repeat;
--

2.51.0

[Brahmajit Das]

The syzkaller report exposed a BUG: “sleeping function called from
invalid context” in sock_map_delete_elem, which happens when
`bpf_test_timer_enter()` disables preemption but the delete path later
invokes a sleeping function while still in that context. Specifically:

- The crash trace shows `bpf_test_timer_enter()` acquiring a
preempt_disable path (via t->mode == NO_PREEMPT), but the symmetric
release path always calls migrate_enable(), mismatching the earlier
disable.
- As a result, preemption remains disabled across the
sock_map_delete_elem path, leading to a sleeping call under an invalid
context. :contentReference[oaicite:0]{index=0}

To fix this, normalize the disable/enable pairing: always use
migrate_disable()/migrate_enable() regardless of t->mode. This ensures
that we never remain with preemption disabled unintentionally when
entering the delete path, and avoids invalid-context sleeping.

Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com

Closes: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
Suggested-by: Yonghong Song <yongho...@linux.dev>
Suggested-by: Menglong Dong <menglo...@linux.dev>
Co-authored-by: Sahil Chandna <chandna.l...@gmail.com>

Signed-off-by: Brahmajit Das <lis...@listout.xyz>
---

Changes in v2:
- remove enum { NO_PREEMPT, NO_MIGRATE } mode
- Using rcu_read_lock_dont_migrate/rcu_read_unlock_migrate

Changes in v1:
- Changes on top of Sahil's initial work based on feedback from
Yonghong's. i.e. remove NO_PREEMPT/NO_MIGRATE in test_run.c and use
migrate_disable()/migrate_enable() universally.
Link: https://lore.kernel.org/all/d0fdced7-a9a5-473e...@linux.dev/

Please also find Sahil's v2 patch:
Link: https://lore.kernel.org/all/20251010075923.408195...@gmail.com/T/
---
net/bpf/test_run.c | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfb03ee0bb62..83f97ee34419 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -29,7 +29,6 @@

#include <trace/events/bpf_test_run.h>

struct bpf_test_timer {
- enum { NO_PREEMPT, NO_MIGRATE } mode;
u32 i;
u64 time_start, time_spent;
};

@@ -37,11 +36,7 @@ struct bpf_test_timer {

static void bpf_test_timer_enter(struct bpf_test_timer *t)
__acquires(rcu)
{

- rcu_read_lock();

- if (t->mode == NO_PREEMPT)
- preempt_disable();
- else
- migrate_disable();

+ rcu_read_lock_dont_migrate();

t->time_start = ktime_get_ns();
}

@@ -51,11 +46,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)

{
t->time_start = 0;

- if (t->mode == NO_PREEMPT)
- preempt_enable();
- else
- migrate_enable();

- rcu_read_unlock();
+ rcu_read_unlock_migrate();
}

static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iterations,
@@ -374,7 +365,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,

{
struct xdp_test_data xdp = { .batch_size = batch_size };
- struct bpf_test_timer t = { .mode = NO_MIGRATE };
+ struct bpf_test_timer t = {};
int ret;

if (!repeat)

@@ -404,7 +395,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,

struct bpf_prog_array_item item = {.prog = prog};
struct bpf_run_ctx *old_ctx;
struct bpf_cg_run_ctx run_ctx;
- struct bpf_test_timer t = { NO_MIGRATE };
+ struct bpf_test_timer t = {};
enum bpf_cgroup_storage_type stype;
int ret;

@@ -1377,7 +1368,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,

const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };
+ struct bpf_test_timer t = {};
u32 size = kattr->test.data_size_in;
struct bpf_flow_dissector ctx = {};
u32 repeat = kattr->test.repeat;

@@ -1445,7 +1436,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,

[syzbot]

Hello,

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

Reported-by: syzbot+1f1fbe...@syzkaller.appspotmail.com
Tested-by: syzbot+1f1fbe...@syzkaller.appspotmail.com

Tested on:

commit: 3a866087 Linux 6.18-rc1
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1017867c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1620e3721dc97c0

dashboard link: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
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=12fd652f980000