media: vidtv: fix NULL pointer dereference in vidtv_channel_pmt_match_sections

In the Linux kernel, the following vulnerability has been resolved:

media: vidtv: fix NULL pointer dereference in vidtv_channel_pmt_match_sections

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