1. ffmpeg
  2. Commit 0b0e87bb544be1926c4ee86c25789d5d6c3c6255
Browse code

atrac3: avoid oversized shifting in decode_bytes()

When `off' is 0, `0x537F6103 << 32' in the following expression invokes
undefined behavior, the result of which is not necessarily 0.

(0x537F6103 >> (off * 8)) | (0x537F6103 << (32 - (off * 8)))

Avoid oversized shifting.

CC: libav-stable@libav.org

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

(cherry picked from commit eba1ff31304e407db3cefd7532108408f364367b)

Xi Wang authored on 2013/03/15 19:31:21
Showing 1 changed files
libavcodec/atrac3.c
History View file @ 0b0e87b
... ... 
@@ -164,7 +164,10 @@ static int decode_bytes(const uint8_t *input, uint8_t *out, int bytes)
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     off = (intptr_t)input & 3;
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     buf = (const uint32_t *)(input - off);
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-    c   = av_be2ne32((0x537F6103 >> (off * 8)) | (0x537F6103 << (32 - (off * 8))));
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+    if (off)
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+        c = av_be2ne32((0x537F6103U >> (off * 8)) | (0x537F6103U << (32 - (off * 8))));
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+    else
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+        c = av_be2ne32(0x537F6103U);
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     bytes += 3 + off;
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     for (i = 0; i < bytes / 4; i++)
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         output[i] = c ^ buf[i];