[gcc r12-5197] libbacktrace: fix UBSAN issues

[gcc r12-5197] libbacktrace: fix UBSAN issues

[Martin Liska]

https://gcc.gnu.org/g:83310a08a2bc52b6e8c3a3e3216b4e723e58c961

commit r12-5197-g83310a08a2bc52b6e8c3a3e3216b4e723e58c961
Author: Martin Liska <mliska@suse.cz>
Date:   Fri Nov 12 14:50:57 2021 +0100

    libbacktrace: fix UBSAN issues
    
    Fix issues mentioned in the PR.
    
            PR libbacktrace/103167
    
    libbacktrace/ChangeLog:
    
            * elf.c (elf_uncompress_lzma_block): Cast to unsigned int.
            (elf_uncompress_lzma): Likewise.
            * xztest.c (test_samples): memcpy only if v > 0.

Diff:
---
 libbacktrace/elf.c    | 32 ++++++++++++++++----------------
 libbacktrace/xztest.c |  2 +-
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/libbacktrace/elf.c b/libbacktrace/elf.c
index 79d56146fc6..8b87b2dd6b9 100644
--- a/libbacktrace/elf.c
+++ b/libbacktrace/elf.c
@@ -3172,10 +3172,10 @@ elf_uncompress_lzma_block (const unsigned char *compressed,
   /* Block header CRC.  */
   computed_crc = elf_crc32 (0, compressed + block_header_offset,
 			    block_header_size - 4);
-  stream_crc = (compressed[off]
-		| (compressed[off + 1] << 8)
-		| (compressed[off + 2] << 16)
-		| (compressed[off + 3] << 24));
+  stream_crc = ((uint32_t)compressed[off]
+		| ((uint32_t)compressed[off + 1] << 8)
+		| ((uint32_t)compressed[off + 2] << 16)
+		| ((uint32_t)compressed[off + 3] << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3785,10 +3785,10 @@ elf_uncompress_lzma (struct backtrace_state *state,
 
   /* Next comes a CRC of the stream flags.  */
   computed_crc = elf_crc32 (0, compressed + 6, 2);
-  stream_crc = (compressed[8]
-		| (compressed[9] << 8)
-		| (compressed[10] << 16)
-		| (compressed[11] << 24));
+  stream_crc = ((uint32_t)compressed[8]
+		| ((uint32_t)compressed[9] << 8)
+		| ((uint32_t)compressed[10] << 16)
+		| ((uint32_t)compressed[11] << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3829,10 +3829,10 @@ elf_uncompress_lzma (struct backtrace_state *state,
 
   /* Before that is a footer CRC.  */
   computed_crc = elf_crc32 (0, compressed + offset, 6);
-  stream_crc = (compressed[offset - 4]
-		| (compressed[offset - 3] << 8)
-		| (compressed[offset - 2] << 16)
-		| (compressed[offset - 1] << 24));
+  stream_crc = ((uint32_t)compressed[offset - 4]
+		| ((uint32_t)compressed[offset - 3] << 8)
+		| ((uint32_t)compressed[offset - 2] << 16)
+		| ((uint32_t)compressed[offset - 1] << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3888,10 +3888,10 @@ elf_uncompress_lzma (struct backtrace_state *state,
   /* Next is a CRC of the index.  */
   computed_crc = elf_crc32 (0, compressed + index_offset,
 			    offset - index_offset);
-  stream_crc = (compressed[offset]
-		| (compressed[offset + 1] << 8)
-		| (compressed[offset + 2] << 16)
-		| (compressed[offset + 3] << 24));
+  stream_crc = ((uint32_t)compressed[offset]
+		| ((uint32_t)compressed[offset + 1] << 8)
+		| ((uint32_t)compressed[offset + 2] << 16)
+		| ((uint32_t)compressed[offset + 3] << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
diff --git a/libbacktrace/xztest.c b/libbacktrace/xztest.c
index b2533cb1804..6c60ff50159 100644
--- a/libbacktrace/xztest.c
+++ b/libbacktrace/xztest.c
@@ -172,7 +172,7 @@ test_samples (struct backtrace_state *state)
 		       tests[i].name, uncompressed_len, v);
 	      ++failures;
 	    }
-	  else if (memcmp (tests[i].uncompressed, uncompressed, v) != 0)
+	  else if (v > 0 && memcmp (tests[i].uncompressed, uncompressed, v) != 0)
 	    {
 	      size_t j;