Re: [Patch] MdeModulePkg BrotliDecompressLib: Add the checker to avoid array out of bound

["Zeng, Star" <star.zeng@intel.com>]

Liming,

They are reported by some static analysis tool, right?
I think you add some information about it in the commit log. You can do that when pushing the patch.

Thanks,
Star
-----Original Message-----
From: Zeng, Star 
Sent: Wednesday, October 17, 2018 4:43 PM
To: Gao, Liming <liming.gao@intel.com>; edk2-devel@lists.01.org
Cc: Zeng, Star <star.zeng@intel.com>
Subject: RE: [edk2] [Patch] MdeModulePkg BrotliDecompressLib: Add the checker to avoid array out of bound

Reviewed-by: Star Zeng <star.zeng@intel.com>


Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Liming Gao
Sent: Tuesday, October 16, 2018 3:27 PM
To: edk2-devel@lists.01.org
Subject: [edk2] [Patch] MdeModulePkg BrotliDecompressLib: Add the checker to avoid array out of bound

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Liming Gao <liming.gao@intel.com>
---
 MdeModulePkg/Library/BrotliCustomDecompressLib/dec/decode.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/MdeModulePkg/Library/BrotliCustomDecompressLib/dec/decode.c b/MdeModulePkg/Library/BrotliCustomDecompressLib/dec/decode.c
index fd42b3b..f3b3cb8 100644
--- a/MdeModulePkg/Library/BrotliCustomDecompressLib/dec/decode.c
+++ b/MdeModulePkg/Library/BrotliCustomDecompressLib/dec/decode.c
@@ -858,6 +858,7 @@ static BROTLI_INLINE uint32_t ReadBlockLength(const HuffmanCode* table,
   uint32_t code;
   uint32_t nbits;
   code = ReadSymbol(table, br);
+  ASSERT (code < BROTLI_NUM_BLOCK_LEN_SYMBOLS);
   nbits = kBlockLengthPrefixCode[code].nbits;  /* nbits == 2..24 */
   return kBlockLengthPrefixCode[code].offset + BrotliReadBits(br, nbits);  } @@ -910,6 +911,7 @@ static BROTLI_NOINLINE void InverseMoveToFrontTransform(
   uint32_t upper_bound = state->mtf_upper_bound;
   uint32_t* mtf = &state->mtf[1];  /* Make mtf[-1] addressable. */
   uint8_t* mtf_u8 = (uint8_t*)mtf;
+  uint8_t* mtf_u8t = mtf_u8 - 1;
   /* Load endian-aware constant. */
   const uint8_t b0123[4] = {0, 1, 2, 3};
   uint32_t pattern;
@@ -928,13 +930,13 @@ static BROTLI_NOINLINE void InverseMoveToFrontTransform(
   for (i = 0; i < v_len; ++i) {
     int index = v[i];
     uint8_t value = mtf_u8[index];
-    upper_bound |= v[i];
+    upper_bound |= (uint32_t) v[i];
     v[i] = value;
-    mtf_u8[-1] = value;
-    do {
+    mtf_u8t[0] = value;
+    while (index >= 0) {
+      mtf_u8t[index + 1] = mtf_u8t[index];
       index--;
-      mtf_u8[index + 1] = mtf_u8[index];
-    } while (index >= 0);
+    }
   }
   /* Remember amount of elements to be reinitialized. */
   state->mtf_upper_bound = upper_bound >> 2; @@ -1566,6 +1568,7 @@ static BROTLI_INLINE BROTLI_BOOL ReadCommandInternal(
   BrotliBitReaderState memento;
   if (!safe) {
     cmd_code = ReadSymbol(s->htree_command, br);
+    ASSERT (cmd_code < BROTLI_NUM_COMMAND_SYMBOLS);
   } else {
     BrotliBitReaderSaveState(br, &memento);
     if (!SafeReadSymbol(s->htree_command, br, &cmd_code)) {
--
2.10.0.windows.1

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