[FFmpeg-devel] [PATCH 19/19] avfilter/af_headphone: Fix segfault upon allocation failure

Andreas Rheinhardt andreas.rheinhardt at gmail.com
Tue Aug 25 17:09:27 EEST 2020

The headphone filter uses a variable number of inpads and allocates them
in its init function; if all goes well, the number of inpads coincides
with a number stored in the filter's private context. Yet if allocating a
subsequent inpad fails, the uninit function nevertheless uses the number
stored in the private context to determine the number of inpads to free
and not the AVFilterContext's nb_inputs. This will lead to an access
beyond the end of the allocated AVFilterContext.input_pads array and
an invalid free.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
This is not the only thing wrong in this filter. Will send a separate
patchset for it.

 libavfilter/af_headphone.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/libavfilter/af_headphone.c b/libavfilter/af_headphone.c
index 552ad84837..751f4ab53d 100644
--- a/libavfilter/af_headphone.c
+++ b/libavfilter/af_headphone.c
@@ -812,7 +812,6 @@ static int config_output(AVFilterLink *outlink)
 static av_cold void uninit(AVFilterContext *ctx)
     HeadphoneContext *s = ctx->priv;
-    int i;
@@ -834,11 +833,9 @@ static av_cold void uninit(AVFilterContext *ctx)
-    for (i = 0; i < s->nb_inputs; i++) {
-        if (ctx->input_pads && i)
-            av_freep(&ctx->input_pads[i].name);
-    }
+    for (unsigned i = 1; i < ctx->nb_inputs; i++)
+        av_freep(&ctx->input_pads[i].name);
 #define OFFSET(x) offsetof(HeadphoneContext, x)

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