[U-Boot] [PATCH 4/6] lzma: correctly bounds-check output buffer

Kees Cook
2013-08-16T14:59:14Z

The output buffer size must be correctly passed to the lzma decoder or
there is a risk of overflowing memory during decompression. Switching
to the LZMA_FINISH_END mode means nothing is left in an unknown state
once the buffer becomes full.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
---
lib/lzma/LzmaTools.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/lzma/LzmaTools.c b/lib/lzma/LzmaTools.c
index 8d1165e11b..0aec2f9 100644
--- a/lib/lzma/LzmaTools.c
+++ b/lib/lzma/LzmaTools.c
@@ -97,15 +97,19 @@ int lzmaBuffToBuffDecompress (unsigned char *outStream, SizeT *uncompressedSize,
g_Alloc.Alloc = SzAlloc;
g_Alloc.Free = SzFree;

+ /* Short-circuit early if we know the buffer can't hold the results. */
+ if (outSizeFull != (SizeT)-1 && *uncompressedSize < outSizeFull)
+ return SZ_ERROR_OUTPUT_EOF;
+
/* Decompress */
- outProcessed = outSizeFull;
+ outProcessed = *uncompressedSize;

WATCHDOG_RESET();

res = LzmaDecode(
outStream, &outProcessed,
inStream + LZMA_DATA_OFFSET, &compressedSize,
- inStream, LZMA_PROPS_SIZE, LZMA_FINISH_ANY, &state, &g_Alloc);
+ inStream, LZMA_PROPS_SIZE, LZMA_FINISH_END, &state, &g_Alloc);
*uncompressedSize = outProcessed;
if (res != SZ_OK) {
return res;
--
1.7.9.5