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apetag: fix error handling in ff_ape_parse_tag()

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The following error handling is broken due to signedness.

    int file_size;
    uint32_t tag_bytes;
    int64_t tag_start;
    ...
    tag_start = file_size - tag_bytes - APE_TAG_FOOTER_BYTES;
    if (tag_start < 0) { ... }

Note that tag_bytes is unsigned, which makes the right-hand side of
`tag_start = ...' unsigned, too.  The 32-bit unsigned value is then
zero-extended to 64 bits.  Therefore, tag_start must be non-negative,
and the check (tag_start < 0) is always false, which breaks the error
handling.  This patch fixes the check.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
Xi Wang 2012-11-14 03:25:41 -05:00 committed by Anton Khirnov
parent 17fecb4a59
commit b655cfefaf
1 changed files with 2 additions and 2 deletions
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4
libavformat/apetag.c
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@ -144,11 +144,11 @@ int64_t ff_ape_parse_tag(AVFormatContext *s)
return 0;
}
tag_start = file_size - tag_bytes - APE_TAG_FOOTER_BYTES;
if (tag_start < 0) {
if (tag_bytes > file_size - APE_TAG_FOOTER_BYTES) {
av_log(s, AV_LOG_ERROR, "Invalid tag size %u.\n", tag_bytes);
return 0;
}
tag_start = file_size - tag_bytes - APE_TAG_FOOTER_BYTES;
fields = avio_rl32(pb); /* number of fields */
if (fields > 65536) {