On Tue Mar 17 17:05:44 2026 +0000, Ruslan Valiyev wrote:
> syzbot reported a general protection fault in
> vidtv_psi_ts_psi_write_into [1].
>
> vidtv_mux_get_pid_ctx() can return NULL, but vidtv_mux_push_si() does
> not check for this before dereferencing the returned pointer to access
> the continuity counter. This leads to a general protection fault when
> accessing a near-NULL address.
>
> The root cause is that vidtv_mux_pid_ctx_init() does not check the
> return value of vidtv_mux_create_pid_ctx_once() for PMT section PIDs.
> If the allocation fails, the PID context is never created, but init
> returns success. The subsequent vidtv_mux_push_si() call then gets
> NULL from vidtv_mux_get_pid_ctx() and crashes.
>
> Fix both the root cause (add error check in vidtv_mux_pid_ctx_init
> for PMT PIDs) and add defensive NULL checks in vidtv_mux_push_si for
> all vidtv_mux_get_pid_ctx() calls.
>
> [1]
> Oops: general protection fault, probably for non-canonical address
> 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> Workqueue: events vidtv_mux_tick
> RIP: 0010:vidtv_psi_ts_psi_write_into+0x54a/0xbc0
> drivers/media/test-drivers/vidtv/vidtv_psi.c:197
> Call Trace:
> <TASK>
> vidtv_psi_table_header_write_into
> drivers/media/test-drivers/vidtv/vidtv_psi.c:799 [inline]
> vidtv_psi_pmt_write_into+0x3b2/0xa70
> drivers/media/test-drivers/vidtv/vidtv_psi.c:1231
> vidtv_mux_push_si+0x932/0xe80
> drivers/media/test-drivers/vidtv/vidtv_mux.c:196
> vidtv_mux_tick+0xe9b/0x1480 drivers/media/test-drivers/vidtv/vidtv_mux.c:408
>
> Fixes: f90cf6079bf67 ("media: vidtv: add a bridge driver")
> Cc: [email protected]
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=814c351d094f4f1a1b86
> Signed-off-by: Ruslan Valiyev <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/test-drivers/vidtv/vidtv_mux.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.c
b/drivers/media/test-drivers/vidtv/vidtv_mux.c
index f0134e38a1fb..ea2ea53102f9 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_mux.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_mux.c
@@ -101,7 +101,8 @@ static int vidtv_mux_pid_ctx_init(struct vidtv_mux *m)
/* add a ctx for all PMT sections */
while (p) {
pid = vidtv_psi_get_pat_program_pid(p);
- vidtv_mux_create_pid_ctx_once(m, pid);
+ if (!vidtv_mux_create_pid_ctx_once(m, pid))
+ goto free;
p = p->next;
}
@@ -170,6 +171,9 @@ static u32 vidtv_mux_push_si(struct vidtv_mux *m)
nit_ctx = vidtv_mux_get_pid_ctx(m, VIDTV_NIT_PID);
eit_ctx = vidtv_mux_get_pid_ctx(m, VIDTV_EIT_PID);
+ if (!pat_ctx || !sdt_ctx || !nit_ctx || !eit_ctx)
+ return 0;
+
pat_args.offset = m->mux_buf_offset;
pat_args.continuity_counter = &pat_ctx->cc;
@@ -186,6 +190,8 @@ static u32 vidtv_mux_push_si(struct vidtv_mux *m)
}
pmt_ctx = vidtv_mux_get_pid_ctx(m, pmt_pid);
+ if (!pmt_ctx)
+ continue;
pmt_args.offset = m->mux_buf_offset;
pmt_args.pmt = m->si.pmt_secs[i];
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