On 11/1/19 5:53 PM, Dafna Hirschfeld wrote:
> Userspace can disable links and create pipelines that
> do not start with a source entity. Trying to stream
> from such a pipeline should fail with -EPIPE
> currently this is not handled and cause kernel crash.
>
> Reproducing the crash:
> media-ctl -d0 -l "5:1->21:0[0]" -v
> v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440
> v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video2
>
> Panic message:
> [ 39.078841][ T248] BUG: kernel NULL pointer dereference, address: 0000000000000000
> [ 39.079338][ T248] #PF: supervisor read access in kernel mode
> [ 39.079704][ T248] #PF: error_code(0x0000) - not-present page
> [ 39.080071][ T248] PGD 0 P4D 0
> [ 39.080279][ T248] Oops: 0000 [#1] SMP PTI
> [ 39.080546][ T248] CPU: 0 PID: 248 Comm: vimc-streamer t Not tainted 5.4.0-rc1+ #17
> [ 39.081030][ T248] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
> [ 39.081779][ T248] RIP: 0010:vimc_sca_process_frame+0xdb/0x210 [vimc]
> [ 39.082191][ T248] Code: 44 8d 0c 28 8b 93 a4 01 00 00 48 8b 8b 98 01 00 00 85 d2 74 40 48 8b 74 24 10 8d 7a ff 4c 01 c9 31 d2 4c 01 fe eb 03 4c 89 c2 <44> 0f b6 04 16 44 88 04 11 4c 8d 42 01 48 39 fa 75 eb 8b 93 a4 01
> [ 39.083436][ T248] RSP: 0018:ffffb15a005abe90 EFLAGS: 00010246
> [ 39.083808][ T248] RAX: 0000000000000000 RBX: ffffa3fdc46d2e00 RCX: ffffb15a02579000
> [ 39.084298][ T248] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
> [ 39.084792][ T248] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> [ 39.085280][ T248] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
> [ 39.085770][ T248] R13: ffffa3fdc46d2ee0 R14: 0000000000000000 R15: 0000000000000000
> [ 39.086258][ T248] FS: 0000000000000000(0000) GS:ffffa3fdc7800000(0000) knlGS:0000000000000000
> [ 39.086806][ T248] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 39.087217][ T248] CR2: 0000000000000000 CR3: 0000000003c92005 CR4: 0000000000360ef0
> [ 39.087706][ T248] Call Trace:
> [ 39.087909][ T248] ? vimc_streamer_pipeline_terminate+0x90/0x90 [vimc]
> [ 39.088318][ T248] vimc_streamer_thread+0x7c/0xe0 [vimc]
> [ 39.088663][ T248] kthread+0x10d/0x130
> [ 39.088919][ T248] ? kthread_park+0x80/0x80
> [ 39.089205][ T248] ret_from_fork+0x35/0x40
> [ 39.089475][ T248] Modules linked in: vimc videobuf2_vmalloc videobuf2_memops v4l2_tpg videobuf2_v4l2 videobuf2_common videodev mc
> [ 39.090208][ T248] CR2: 0000000000000000
> [ 39.090463][ T248] ---[ end trace 697650fefbf78bee ]---
> [ 39.090796][ T248] RIP: 0010:vimc_sca_process_frame+0xdb/0x210 [vimc]
> [ 39.091209][ T248] Code: 44 8d 0c 28 8b 93 a4 01 00 00 48 8b 8b 98 01 00 00 85 d2 74 40 48 8b 74 24 10 8d 7a ff 4c 01 c9 31 d2 4c 01 fe eb 03 4c 89 c2 <44> 0f b6 04 16 44 88 04 11 4c 8d 42 01 48 39 fa 75 eb 8b 93 a4 01
> [ 39.092417][ T248] RSP: 0018:ffffb15a005abe90 EFLAGS: 00010246
> [ 39.092789][ T248] RAX: 0000000000000000 RBX: ffffa3fdc46d2e00 RCX: ffffb15a02579000
> [ 39.093278][ T248] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
> [ 39.093766][ T248] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> [ 39.094254][ T248] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
> [ 39.094742][ T248] R13: ffffa3fdc46d2ee0 R14: 0000000000000000 R15: 0000000000000000
> [ 39.095309][ T248] FS: 0000000000000000(0000) GS:ffffa3fdc7800000(0000) knlGS:0000000000000000
> [ 39.095974][ T248] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 39.096372][ T248] CR2: 0000000000000000 CR3: 0000000003c92005 CR4: 0000000000360ef0
>
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>
Acked-by: Helen Koike <helen.koike@xxxxxxxxxxxxx>
Thanks!
Helen
> ---
> Changes since v5:
> 1. change the documentation of vimc_is_source
> 2. rewrite the patch so that it has the minimal code that fixes the crash
>
> drivers/media/platform/vimc/vimc-common.c | 10 ++++++++++
> drivers/media/platform/vimc/vimc-common.h | 8 ++++++++
> drivers/media/platform/vimc/vimc-streamer.c | 13 +++++++++++--
> 3 files changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/vimc/vimc-common.c b/drivers/media/platform/vimc/vimc-common.c
> index 2a0c40e9ae88..64aa71230522 100644
> --- a/drivers/media/platform/vimc/vimc-common.c
> +++ b/drivers/media/platform/vimc/vimc-common.c
> @@ -164,6 +164,16 @@ static const struct vimc_pix_map vimc_pix_map_list[] = {
> },
> };
>
> +bool vimc_is_source(struct media_entity *ent)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < ent->num_pads; i++)
> + if (ent->pads[i].flags & MEDIA_PAD_FL_SINK)
> + return false;
> + return true;
> +}
> +
> const struct vimc_pix_map *vimc_pix_map_by_index(unsigned int i)
> {
> if (i >= ARRAY_SIZE(vimc_pix_map_list))
> diff --git a/drivers/media/platform/vimc/vimc-common.h b/drivers/media/platform/vimc/vimc-common.h
> index c75401a36312..91375c5cdc2b 100644
> --- a/drivers/media/platform/vimc/vimc-common.h
> +++ b/drivers/media/platform/vimc/vimc-common.h
> @@ -139,6 +139,14 @@ struct vimc_ent_config {
> void (*rm)(struct vimc_device *vimc, struct vimc_ent_device *ved);
> };
>
> +/**
> + * vimc_is_source - returns true if the entity has only source pads
> + *
> + * @ent: pointer to &struct media_entity
> + *
> + */
> +bool vimc_is_source(struct media_entity *ent);
> +
> /* prototypes for vimc_ent_config add and rm hooks */
> struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
> const char *vcfg_name);
> diff --git a/drivers/media/platform/vimc/vimc-streamer.c b/drivers/media/platform/vimc/vimc-streamer.c
> index 1349be188a5b..cd6b55433c9e 100644
> --- a/drivers/media/platform/vimc/vimc-streamer.c
> +++ b/drivers/media/platform/vimc/vimc-streamer.c
> @@ -104,9 +104,18 @@ static int vimc_streamer_pipeline_init(struct vimc_stream *stream,
> }
>
> entity = vimc_get_source_entity(ved->ent);
> - /* Check if the end of the pipeline was reached*/
> - if (!entity)
> + /* Check if the end of the pipeline was reached */
> + if (!entity) {
> + /* the first entity of the pipe should be source only */
> + if (!vimc_is_source(ved->ent)) {
> + dev_err(ved->dev,
> + "first entity in the pipe '%s' is not a source\n",
> + ved->ent->name);
> + vimc_streamer_pipeline_terminate(stream);
> + return -EPIPE;
> + }
> return 0;
> + }
>
> /* Get the next device in the pipeline */
> if (is_media_entity_v4l2_subdev(entity)) {
>
