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lavc: check for overflow in init_get_bits

Fix an undefined behaviour and make the function return a proper
error in case of overflow.

CC: libav-stable@libav.org
(cherry picked from commit d9cf5f5)

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
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commit 7a2ee770f520ae4fd5f009cfc361a18e993dec91 1 parent fadebd2
@lu-zero lu-zero authored
Showing with 15 additions and 7 deletions.
  1. +15 −7 libavcodec/get_bits.h
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22 libavcodec/get_bits.h
@@ -362,20 +362,27 @@ static inline int check_marker(GetBitContext *s, const char *msg)
}
/**
- * Inititalize GetBitContext.
- * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger than the actual read bits
- * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
+ * Initialize GetBitContext.
+ * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
+ * larger than the actual read bits because some optimized bitstream
+ * readers read 32 or 64 bit at once and could read over the end
* @param bit_size the size of the buffer in bits
+ * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
*/
-static inline void init_get_bits(GetBitContext *s, const uint8_t *buffer,
- int bit_size)
+static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
+ int bit_size)
{
- int buffer_size = (bit_size+7)>>3;
- if (buffer_size < 0 || bit_size < 0) {
+ int buffer_size;
+ int ret = 0;
+
+ if (bit_size > INT_MAX - 7 || bit_size <= 0) {
buffer_size = bit_size = 0;
buffer = NULL;
+ ret = AVERROR_INVALIDDATA;
}
+ buffer_size = (bit_size + 7) >> 3;
+
s->buffer = buffer;
s->size_in_bits = bit_size;
#if !UNCHECKED_BITSTREAM_READER
@@ -383,6 +390,7 @@ static inline void init_get_bits(GetBitContext *s, const uint8_t *buffer,
#endif
s->buffer_end = buffer + buffer_size;
s->index = 0;
+ return ret;
}
static inline void align_get_bits(GetBitContext *s)
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