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[libopenapv] Fix signed overflow in VLC decoding #213

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[libopenapv] Fix signed overflow in VLC decoding #213

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2 changes: 2 additions & 0 deletions src/oapv_vlc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -687,6 +687,7 @@ static int dec_vlc_read_1bit_read(oapv_bs_t *bs)
}
else {
k++;
oapv_assert_rv(k < 30, -1);
}
}
}
Expand Down Expand Up @@ -733,6 +734,7 @@ static int dec_vlc_read(oapv_bs_t *bs, int k)
break;
}
else {
oapv_assert_rv(k < 31, -1);
symbol += (1 << k);
k++;
}
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2 changes: 1 addition & 1 deletion src/oapv_vlc.h
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Expand Up @@ -36,7 +36,7 @@
#include "oapv_metadata.h"

#define KPARAM_DC(level) oapv_min((level)>>1, OAPV_KPARAM_DC_MAX)
#define KPARAM_AC(level) oapv_min((level)>>2, OAPV_KPARAM_AC_MAX)
#define KPARAM_AC(level) oapv_clip3(OAPV_KPARAM_AC_MIN, OAPV_KPARAM_AC_MAX, (level)>>2)

@kpchoi kpchoi Jun 15, 2026

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Level is always positive and monotonically increasing. Camparing with min value is not required.

@fkyslov fkyslov Jun 16, 2026

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Unless it overflows. This code prevents crash (because of MIN_INT) in case of (unintended overflow)

@kpchoi kpchoi Jun 17, 2026

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It is difficult to understand why it can prevent crash. as I mentioned, level is always positive. and it is limited to some value.

#define KPARAM_RUN(run) oapv_min((run)>>2, OAPV_KPARAM_RUN_MAX)

void oapve_set_frame_header(oapve_ctx_t * ctx, oapv_fh_t * fh);
Expand Down