[libav-stable] atrac3: avoid oversized shifting in decode_bytes()

Xi Wang git at libav.org
Fri Mar 15 13:05:39 CET 2013


Module: libav
Branch: master
Commit: eba1ff31304e407db3cefd7532108408f364367b

Author:    Xi Wang <xi.wang at gmail.com>
Committer: Luca Barbato <lu_zero at gentoo.org>
Date:      Fri Mar 15 06:31:21 2013 -0400

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 at libav.org

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

---

 libavcodec/atrac3.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/libavcodec/atrac3.c b/libavcodec/atrac3.c
index da0bff0..a52c5c6 100644
--- a/libavcodec/atrac3.c
+++ b/libavcodec/atrac3.c
@@ -163,7 +163,10 @@ static int decode_bytes(const uint8_t *input, uint8_t *out, int bytes)
 
     off = (intptr_t)input & 3;
     buf = (const uint32_t *)(input - off);
-    c   = av_be2ne32((0x537F6103 >> (off * 8)) | (0x537F6103 << (32 - (off * 8))));
+    if (off)
+        c = av_be2ne32((0x537F6103U >> (off * 8)) | (0x537F6103U << (32 - (off * 8))));
+    else
+        c = av_be2ne32(0x537F6103U);
     bytes += 3 + off;
     for (i = 0; i < bytes / 4; i++)
         output[i] = c ^ buf[i];



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