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avfilter/af_pan: fix sscanf() return value checks in parse_channel_name

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sscanf() returns EOF (-1) on input failure, which is non-zero and
passes a bare truthy check. When this happens, the %n directive is
never processed, so len stays uninitialized. Using that value to
advance the arg pointer causes an out-of-bounds read and crash.

Check for >= 1 instead, matching the fix applied to the other
sscanf() call in init() by commit b5b6391d64.

Fixes: https://code.ffmpeg.org/FFmpeg/FFmpeg/issues/22451
Signed-off-by: marcos ashton <marcosashiglesias@gmail.com>
This commit is contained in:
marcos ashton
2026-03-20 23:49:25 +00:00
committed by michaelni
parent 442e6c80bf
commit a43ea8bff7
1 changed files with 2 additions and 2 deletions
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4
libavfilter/af_pan.c
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@@ -70,7 +70,7 @@ static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
skip_spaces(arg);
/* try to parse a channel name, e.g. "FL" */
if (sscanf(*arg, "%7[A-Z]%n", buf, &len)) {
if (sscanf(*arg, "%7[A-Z]%n", buf, &len) >= 1) {
channel_id = av_channel_from_string(buf);
if (channel_id < 0)
return channel_id;
@@ -81,7 +81,7 @@ static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
return 0;
}
/* try to parse a channel number, e.g. "c2" */
if (sscanf(*arg, "c%d%n", &channel_id, &len) &&
if (sscanf(*arg, "c%d%n", &channel_id, &len) >= 1 &&
channel_id >= 0 && channel_id < MAX_CHANNELS) {
*rchannel = channel_id;
*rnamed = 0;