[PATCH RESEND] PCI/AER: Check for NULL aer_info before ratelimiting in pci_print_aer()

[Breno Leitao]

Hello Christophe,

On Mon, Sep 29, 2025 at 07:01:43PM +0200, Christophe Leroy wrote:
> Le 29/09/2025 à 11:15, Breno Leitao a écrit :
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index e286c197d7167..55abc5e17b8b1 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -786,6 +786,9 @@ static void pci_rootport_aer_stats_incr(struct pci_dev *pdev,
> >   static int aer_ratelimit(struct pci_dev *dev, unsigned int severity)
> >   {
> > +	if (!dev->aer_info)
> > +		return 1;
> > +
> 
> This is a static function, it cannot be called from outside aer.c . Why do
> you need such a check ?

I have more than 5 hosts crash in recent kernel due to this issue. This
is causing real crashes.

	[30745.821301] [ T964809] BUG: kernel NULL pointer dereference, address: 0000000000000264
	[30745.835249] [ T964809] #PF: supervisor read access in kernel mode
	[30745.845541] [ T964809] #PF: error_code(0x0000) - not-present page
	[30745.855831] [ T964809] PGD 7a26aa067 P4D 7a26aa067 PUD 2a807a067 PMD 0
	[30745.867267] [ T964809] Oops: Oops: 0000 [#1] SMP
	[30745.900469] [ T964809] Tainted: [S]=CPU_OUT_OF_SPEC, [E]=UNSIGNED_MODULE
	[30745.911999] [ T964809] Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020
	[30745.929557] [ T964809] Workqueue: events aer_recover_work_func
	[30745.939339] [     T964809] RIP: 0010:___ratelimit (lib/ratelimit.c:33)
	[30745.947896] [ T964809] Code: 89 06 48 8d 45 10 48 89 46 08 48 89 e0 48 89 46 10 48 89 df e8 18 48 0d 00 48 8d 65 f8 5b 5d c3 cc 55 41 57 41 56 41 54 53 50 <4c> 63 77 04 4d 85 f6 0f 9e c0 8b 5f 08 85 db 0f 9e c1 08 c1 80 f9
	All code
	========
	0:	89 06                	mov    %eax,(%rsi)
	2:	48 8d 45 10          	lea    0x10(%rbp),%rax
	6:	48 89 46 08          	mov    %rax,0x8(%rsi)
	a:	48 89 e0             	mov    %rsp,%rax
	d:	48 89 46 10          	mov    %rax,0x10(%rsi)
	11:	48 89 df             	mov    %rbx,%rdi
	14:	e8 18 48 0d 00       	call   0xd4831
	19:	48 8d 65 f8          	lea    -0x8(%rbp),%rsp
	1d:	5b                   	pop    %rbx
	1e:	5d                   	pop    %rbp
	1f:	c3                   	ret
	20:	cc                   	int3
	21:	55                   	push   %rbp
	22:	41 57                	push   %r15
	24:	41 56                	push   %r14
	26:	41 54                	push   %r12
	28:	53                   	push   %rbx
	29:	50                   	push   %rax
	2a:*	4c 63 77 04          	movslq 0x4(%rdi),%r14		<-- trapping instruction
	2e:	4d 85 f6             	test   %r14,%r14
	31:	0f 9e c0             	setle  %al
	34:	8b 5f 08             	mov    0x8(%rdi),%ebx
	37:	85 db                	test   %ebx,%ebx
	39:	0f 9e c1             	setle  %cl
	3c:	08 c1                	or     %al,%cl
	3e:	80                   	.byte 0x80
	3f:	f9                   	stc

	Code starting with the faulting instruction
	===========================================
	0:	4c 63 77 04          	movslq 0x4(%rdi),%r14
	4:	4d 85 f6             	test   %r14,%r14
	7:	0f 9e c0             	setle  %al
	a:	8b 5f 08             	mov    0x8(%rdi),%ebx
	d:	85 db                	test   %ebx,%ebx
	f:	0f 9e c1             	setle  %cl
	12:	08 c1                	or     %al,%cl
	14:	80                   	.byte 0x80
	15:	f9                   	stc
	[30745.985517] [ T964809] RSP: 0018:ffffc9002a10fc88 EFLAGS: 00010206
	[30745.996094] [ T964809] RAX: 0000000000000002 RBX: 0000000000000002 RCX: ffffffff8260c509
	[30746.010396] [ T964809] RDX: 0000000000000000 RSI: ffffffff825f37b7 RDI: 0000000000000260
	[30746.024710] [ T964809] RBP: 0000000000000000 R08: 8080808080808080 R09: 0000000000000000
	[30746.039044] [ T964809] R10: ffffc9002a10fcf0 R11: 8080000000000000 R12: 0000000000000000
	[30746.053349] [ T964809] R13: 0000000000000000 R14: ffff8882851f4000 R15: ffffc90000c312e0
	[30746.067649] [ T964809] FS:  0000000000000000(0000) GS:ffff8890fa91e000(0000) knlGS:0000000000000000
	[30746.083875] [ T964809] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	[30746.095394] [ T964809] CR2: 0000000000000264 CR3: 00000008150b6002 CR4: 00000000007726f0
	[30746.109695] [ T964809] PKRU: 55555554
	[30746.115123] [ T964809] Call Trace:
	[30746.120028] [ T964809]  <TASK>
	[30746.124253] [     T964809] pci_print_aer (drivers/pci/pcie/aer.c:929)
	[30746.140335] [     T964809] aer_recover_work_func (drivers/pci/pcie/aer.c:1181)
	[30746.149070] [     T964809] process_scheduled_works (kernel/workqueue.c:3243 kernel/workqueue.c:3321)
	[30746.158326] [     T964809] ? worker_thread (kernel/workqueue.c:3355)
	[30746.166195] [     T964809] worker_thread (./include/linux/list.h:373 kernel/workqueue.c:946 kernel/workqueue.c:3403)
	[30746.173718] [     T964809] kthread (kernel/kthread.c:466)
	[30746.180018] [     T964809] ? kick_pool (kernel/workqueue.c:3348)
	[30746.187183] [     T964809] ? finish_task_switch (./include/linux/perf_event.h:? kernel/sched/core.c:5260)
	[30746.195911] [     T964809] ? housekeeping_affine (kernel/kthread.c:413)
	[30746.204502] [     T964809] ret_from_fork (arch/x86/kernel/process.c:154)
	[30746.211842] [     T964809] ? housekeeping_affine (kernel/kthread.c:413)
	[30746.220400] [     T964809] ret_from_fork_asm (arch/x86/entry/entry_64.S:258)


This stack is based on commit 038d61fd64227  ("Linux 6.16").

> I a check was to be made it should be in pci_aer_init() and in fact if
> kmalloc fails then all the probe should be made to fail.

Ok, the stack is not going through pci_aer_init(), but, through
aer_recover_work_func() -> pci_print_aer().