[syzbot] [kernel?] WARNING in hrtimer_forward (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 443574b03387 riscv, bpf: Fix kfunc parameters incompatibil..
git tree: bpf
console output: https://syzkaller.appspot.com/x/log.txt?x=1579f7b1180000
kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=d1ae9c954f73570e7b58
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3f355021a085/disk-443574b0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/44cf4de7472a/vmlinux-443574b0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a99a36c7ad65/bzImage-443574b0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d1ae9c...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 11239 at kernel/time/hrtimer.c:1053 hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053
Modules linked in:
CPU: 1 PID: 11239 Comm: syz-executor.1 Not tainted 6.8.0-syzkaller-05236-g443574b03387 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053
Code: 00 49 89 1e 48 8b 04 24 eb 07 e8 2b a4 12 00 31 c0 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 11 a4 12 00 90 <0f> 0b 90 eb e0 4c 89 f0 31 d2 49 f7 f4 48 89 04 24 49 89 c6 4d 0f
RSP: 0018:ffffc90000a08bf8 EFLAGS: 00010246
RAX: ffffffff81824c5f RBX: 0000000000000001 RCX: ffff88805fe18000
RDX: 0000000000000100 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000003636b41721 R08: ffffffff81824af3 R09: 1ffffffff1f0d5cd
R10: dffffc0000000000 R11: ffffffff81353f80 R12: 00000000061a8000
R13: ffff88805e27ef38 R14: 00000000cb354006 R15: 1ffff1100bc4fde3
FS: 00007f4b92fa26c0(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7730ed5690 CR3: 0000000047bcc000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
hrtimer_forward_now include/linux/hrtimer.h:355 [inline]
mac80211_hwsim_beacon+0x192/0x1f0 drivers/net/wireless/virtual/mac80211_hwsim.c:2335
__run_hrtimer kernel/time/hrtimer.c:1692 [inline]
__hrtimer_run_queues+0x595/0xd00 kernel/time/hrtimer.c:1756
hrtimer_run_softirq+0x19a/0x2c0 kernel/time/hrtimer.c:1773
__do_softirq+0x2bc/0x943 kernel/softirq.c:554
invoke_softirq kernel/softirq.c:428 [inline]
__irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:bpf_prog_is_offloaded include/linux/bpf.h:2972 [inline]
RIP: 0010:do_check+0x7a14/0x10740 kernel/bpf/verifier.c:17669
Code: 00 00 00 00 00 fc ff df 48 8b 1b b8 fa 00 00 00 48 01 c3 48 89 d8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 da 4d 00 00 0f b6 1b <31> ff 89 de e8 a3 0a eb ff 85 db 74 5a 48 ba 00 00 00 00 00 fc ff
RSP: 0018:ffffc90005336dc0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000040000
RDX: ffffc9000c2c8000 RSI: 000000000000a51a RDI: 000000000000a51b
RBP: ffffc90005337120 R08: ffffffff81a9e50d R09: 1ffff1100bfc3000
R10: dffffc0000000000 R11: ffffed100bfc3001 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffc90005337080 R15: ffff88805fe18000
do_check_common+0x14bd/0x1dd0 kernel/bpf/verifier.c:20508
do_check_main kernel/bpf/verifier.c:20599 [inline]
bpf_check+0x126eb/0x18fe0 kernel/bpf/verifier.c:21269
bpf_prog_load+0x1667/0x20f0 kernel/bpf/syscall.c:2895
__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: 0033:0x7f4b9227de69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4b92fa20c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f4b923ac120 RCX: 00007f4b9227de69
RDX: 0000000000000048 RSI: 00000000200054c0 RDI: 0000000000000005
RBP: 00007f4b922ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f4b923ac120 R15: 00007ffdcb39eb48
</TASK>
----------------
Code disassembly (best guess), 7 bytes skipped:
0: df 48 8b fisttps -0x75(%rax)
3: 1b b8 fa 00 00 00 sbb 0xfa(%rax),%edi
9: 48 01 c3 add %rax,%rbx
c: 48 89 d8 mov %rbx,%rax
f: 48 c1 e8 03 shr $0x3,%rax
13: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
18: 84 c0 test %al,%al
1a: 0f 85 da 4d 00 00 jne 0x4dfa
20: 0f b6 1b movzbl (%rbx),%ebx
* 23: 31 ff xor %edi,%edi <-- trapping instruction
25: 89 de mov %ebx,%esi
27: e8 a3 0a eb ff call 0xffeb0acf
2c: 85 db test %ebx,%ebx
2e: 74 5a je 0x8a
30: 48 rex.W
31: ba 00 00 00 00 mov $0x0,%edx
36: 00 fc add %bh,%ah
38: ff .byte 0xff


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[Thomas Gleixner]

On Mon, Apr 08 2024 at 19:46, syzbot wrote:
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 11239 at kernel/time/hrtimer.c:1053 hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053

> RIP: 0010:hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053

> Call Trace:
> <IRQ>
> hrtimer_forward_now include/linux/hrtimer.h:355 [inline]
> mac80211_hwsim_beacon+0x192/0x1f0 drivers/net/wireless/virtual/mac80211_hwsim.c:2335
> __run_hrtimer kernel/time/hrtimer.c:1692 [inline]
> __hrtimer_run_queues+0x595/0xd00 kernel/time/hrtimer.c:1756
> hrtimer_run_softirq+0x19a/0x2c0 kernel/time/hrtimer.c:1773
> __do_softirq+0x2bc/0x943 kernel/softirq.c:554
> invoke_softirq kernel/softirq.c:428 [inline]
> __irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
> irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
> instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
> sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
> </IRQ>

The code which arms the timer is not serialized against the callback so
the following can happen:

CPU1 CPU2

__run_hrtimer(timer)
if (!hrtimer_queued(timer))
hrtimer_start(timer);

hrtimer_forward(timer)
WARN_ON(hrtimer_queued(timer)

This really wants to use hrtimer_active() which takes the running
callback into account.

Thanks,

tglx

--- a/drivers/net/wireless/virtual/mac80211_hwsim.c
+++ b/drivers/net/wireless/virtual/mac80211_hwsim.c
@@ -2422,7 +2422,7 @@ static int mac80211_hwsim_config(struct

if (!data->started || !link_data->beacon_int) {
hrtimer_cancel(&link_data->beacon_timer);
- } else if (!hrtimer_is_queued(&link_data->beacon_timer)) {
+ } else if (!hrtimer_is_active(&link_data->beacon_timer)) {
u64 tsf = mac80211_hwsim_get_tsf(hw, NULL);
u32 bcn_int = link_data->beacon_int;
u64 until_tbtt = bcn_int - do_div(tsf, bcn_int);
@@ -2517,7 +2517,7 @@ static void mac80211_hwsim_link_info_cha
info->enable_beacon, info->beacon_int);
vp->bcn_en = info->enable_beacon;
if (data->started &&
- !hrtimer_is_queued(&link_data->beacon_timer) &&
+ !hrtimer_is_active(&link_data->beacon_timer) &&
info->enable_beacon) {
u64 tsf, until_tbtt;
u32 bcn_int;

[Hillf Danton]

On Tue, 09 Apr 2024 12:46:31 +0200 Thomas Gleixner <tg...@linutronix.de>

Then the race window is still open with hrtimer_active() and serialization
outside hrtimer is needed.

CPU1 CPU2
--- ---
if (!hrtimer_is_active(timer))
if (!hrtimer_is_active(timer))
hrtimer_start(timer);
__run_hrtimer(timer)
hrtimer_start(timer);
hrtimer_forward(timer)
WARN_ON(hrtimer_queued(timer))