[PATCH] media: vidtv: fix NULL pointer dereference in vidtv_channel_pmt_match_sections

[Ruslan Valiyev <linuxoid@gmail.com>]

syzbot reported a general protection fault in vidtv_psi_desc_assign [1].

vidtv_psi_pmt_stream_init() can return NULL on memory allocation
failure, but vidtv_channel_pmt_match_sections() does not check for
this. When tail is NULL, the subsequent call to
vidtv_psi_desc_assign(&tail->descriptor, desc) dereferences a NULL
pointer offset, causing a general protection fault.

Add a NULL check after vidtv_psi_pmt_stream_init(). On failure, clean
up the already-allocated stream chain and return.

[1]
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:vidtv_psi_desc_assign+0x24/0x90 drivers/media/test-drivers/vidtv/vidtv_psi.c:629
Call Trace:
 <TASK>
 vidtv_channel_pmt_match_sections drivers/media/test-drivers/vidtv/vidtv_channel.c:349 [inline]
 vidtv_channel_si_init+0x1445/0x1a50 drivers/media/test-drivers/vidtv/vidtv_channel.c:479
 vidtv_mux_init+0x526/0xbe0 drivers/media/test-drivers/vidtv/vidtv_mux.c:519
 vidtv_start_streaming drivers/media/test-drivers/vidtv/vidtv_bridge.c:194 [inline]
 vidtv_start_feed+0x33e/0x4d0 drivers/media/test-drivers/vidtv/vidtv_bridge.c:239

Fixes: f90cf6079bf67 ("media: vidtv: add a bridge driver")
Cc: stable@vger.kernel.org
Reported-by: syzbot+1f5bcc7c919ec578777a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1f5bcc7c919ec578777a
Signed-off-by: Ruslan Valiyev <linuxoid@gmail.com>
---
 drivers/media/test-drivers/vidtv/vidtv_channel.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/test-drivers/vidtv/vidtv_channel.c b/drivers/media/test-drivers/vidtv/vidtv_channel.c
index da20657adc747..5f8c3af871711 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_channel.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_channel.c
@@ -341,6 +341,10 @@ vidtv_channel_pmt_match_sections(struct vidtv_channel *channels,
 					tail = vidtv_psi_pmt_stream_init(tail,
 									 s->type,
 									 e_pid);
+					if (!tail) {
+						vidtv_psi_pmt_stream_destroy(head);
+						return;
+					}
 
 					if (!head)
 						head = tail;
-- 
2.43.0