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Message-ID: <87jzpt3ljl.fsf@baylibre.com>
Date: Mon, 04 Dec 2023 18:49:34 +0100
From: Mattijs Korpershoek <mkorpershoek@...libre.com>
To: Nicolas Dufresne <nicolas@...fresne.ca>,
Nas Chung <nas.chung@...psnmedia.com>,
Jackson Lee <jackson.lee@...psnmedia.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Guillaume La Roque <glaroque@...libre.com>,
Brandon Brnich <b-brnich@...com>,
Sebastian Fricke <sebastian.fricke@...labora.com>,
Nicolas Dufresne <nicolas.dufresne@...labora.com>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: chips-media: wave5: fix panic on decoding
DECODED_IDX_FLAG_SKIP
Hi Nicolas,
Thank you for your review.
On Fri, Dec 01, 2023 at 15:18, Nicolas Dufresne <nicolas@...fresne.ca> wrote:
> Hi Mattijs,
>
> Le mercredi 29 novembre 2023 à 11:37 +0100, Mattijs Korpershoek a écrit :
>> The display frame region information received from the vpu also
>> contains the frame display index: info->index_frame_display.
>>
>> This index, being a s32, can be negative when a skip option is passed.
>> In that case, its value is DECODED_IDX_FLAG_SKIP (-2).
>>
>> When disp_idx == -2, the following exception occurs:
>>
>> [ 1530.782246][ T1900] Hardware name: Texas Instruments AM62P5 SK (DT)
>> [ 1530.788501][ T1900] pstate: a0400005 (NzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> [ 1530.796144][ T1900] pc : wave5_vpu_dec_get_output_info+0x300/0x308 [wave5]
>> [ 1530.803060][ T1900] lr : wave5_vpu_dec_get_output_info+0x80/0x308 [wave5]
>> [ 1530.809873][ T1900] sp : ffffffc00b85bc00
>> [ 1530.813872][ T1900] x29: ffffffc00b85bc00 x28: 0000000000000000 x27: 0000000000000001
>> [ 1530.821695][ T1900] x26: 00000000fffffffd x25: 00000000ffffffff x24: ffffff8812820000
>> [ 1530.829516][ T1900] x23: ffffff88199f7840 x22: ffffff8873f5e000 x21: ffffffc00b85bc58
>> [ 1530.837336][ T1900] x20: 0000000000000000 x19: ffffff88199f7920 x18: ffffffc00a899030
>> [ 1530.845156][ T1900] x17: 00000000529c6ef0 x16: 00000000529c6ef0 x15: 0000000000198487
>> [ 1530.852975][ T1900] x14: ffffffc009f2b650 x13: 0000000000058016 x12: 0000000005000000
>> [ 1530.860795][ T1900] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
>> [ 1530.868615][ T1900] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000004086
>> [ 1530.876434][ T1900] x5 : 0000000000000001 x4 : ffffffc001454b94 x3 : ffffffc001454d94
>> [ 1530.884256][ T1900] x2 : ffffffc00b8201d0 x1 : 0000000000000020 x0 : 0000000000000000
>> [ 1530.892087][ T1900] Call trace:
>> [ 1530.895225][ T1900] wave5_vpu_dec_get_output_info+0x300/0x308 [wave5]
>> [ 1530.901788][ T1900] wave5_vpu_dec_finish_decode+0x6c/0x3dc [wave5]
>> [ 1530.908081][ T1900] wave5_vpu_irq_thread+0x140/0x168 [wave5]
>> [ 1530.913856][ T1900] irq_thread_fn+0x44/0xa4
>> [ 1530.918154][ T1900] irq_thread+0x15c/0x288
>> [ 1530.922330][ T1900] kthread+0x104/0x1d4
>> [ 1530.926247][ T1900] ret_from_fork+0x10/0x20
>> [ 1530.930520][ T1900] Code: 2a1f03ea 2a1f03eb 35ffef2c 17ffff74 (d42aa240)
>> [ 1530.937296][ T1900] ---[ end trace 0000000000000000 ]---
>> [ 1530.942596][ T1900] Kernel panic - not syncing: BRK handler: Fatal exception
>> [ 1530.949629][ T1900] SMP: stopping secondary CPUs
>> [ 1530.954244][ T1900] Kernel Offset: disabled
>> [ 1530.958415][ T1900] CPU features: 0x00,00000000,00800184,0000421b
>> [ 1530.964496][ T1900] Memory Limit: none
>>
>> Move the disp_info assignment after testing that the index is positive
>> to avoid the exception.
>>
>> Fixes: 45d1a2b93277 ("media: chips-media: wave5: Add vpuapi layer")
>> Signed-off-by: Mattijs Korpershoek <mkorpershoek@...libre.com>
>> ---
>> drivers/media/platform/chips-media/wave5/wave5-vpuapi.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
>> index 86b3993722db..1a3efb638dde 100644
>> --- a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
>> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
>> @@ -508,8 +508,8 @@ int wave5_vpu_dec_get_output_info(struct vpu_instance *inst, struct dec_output_i
>> info->rc_decoded = rect_info;
>>
>> disp_idx = info->index_frame_display;
>> - disp_info = &p_dec_info->dec_out_info[disp_idx];
>> if (info->index_frame_display >= 0 && info->index_frame_display < WAVE5_MAX_FBS) {
>> + disp_info = &p_dec_info->dec_out_info[disp_idx];
>
> I could not reproduce the crash, it probably depends on the compiler version and
> compiler options. This negative index should normally generate a pointer, even
> if that points to bad location. I'd like to understand how that lead to a crash.
> If you have further information on this, I really like to get to the bottom on
> these subjects.
I can reproduce it consistently with my setup:
https://pastebin.com/0Mdfw1EC
Here is a copy of the .config when my kernel is build:
https://pastebin.com/RHxLV8cf
I build the kernel via KLeaf (Android's way of building kernels) so I'm
not sure how I can provide you with the exact compile command.
I do know that LTO is used, if that gives any hint.
If prefer chatting about this, I'm also reachable on irc (oftc.net, nickname:
mkorpershoek)
Let me know if other information is needed to get to the bottom on this.
>
> Meanwhile, this fix is obviously correct, we should not do that unless we have a
> valid index.
>
> Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
>
>> if (info->index_frame_display != info->index_frame_decoded) {
>> /*
>> * when index_frame_decoded < 0, and index_frame_display >= 0
>>
>> ---
>> base-commit: a00b3f296eac3d43328615c3113e1a74143fc67a
>> change-id: 20231129-wave5-panic-82ea2d30042f
>>
>> Best regards,
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