[gcc(refs/users/marxin/heads/PR103167-libbacktrace-ubsan-asan)] libbacktrace: fix UBSAN issues

[gcc(refs/users/marxin/heads/PR103167-libbacktrace-ubsan-asan)] libbacktrace: fix UBSAN issues

[Martin Liska]

https://gcc.gnu.org/g:102722133c81481b98dbe583f772667a0f45a67d

commit 102722133c81481b98dbe583f772667a0f45a67d
Author: Martin Liska <mliska@suse.cz>
Date:   Wed Nov 10 16:16:19 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.
    
    Co-Authored-By: Andrew Pinski <apinski@marvell.com>

Diff:
---
 libbacktrace/elf.c    | 8 ++++----
 libbacktrace/xztest.c | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libbacktrace/elf.c b/libbacktrace/elf.c
index 79d56146fc6..e69ac41c88b 100644
--- a/libbacktrace/elf.c
+++ b/libbacktrace/elf.c
@@ -3175,7 +3175,7 @@ elf_uncompress_lzma_block (const unsigned char *compressed,
   stream_crc = (compressed[off]
 		| (compressed[off + 1] << 8)
 		| (compressed[off + 2] << 16)
-		| (compressed[off + 3] << 24));
+		| ((unsigned)(compressed[off + 3]) << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3788,7 +3788,7 @@ elf_uncompress_lzma (struct backtrace_state *state,
   stream_crc = (compressed[8]
 		| (compressed[9] << 8)
 		| (compressed[10] << 16)
-		| (compressed[11] << 24));
+		| ((unsigned)(compressed[11]) << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3832,7 +3832,7 @@ elf_uncompress_lzma (struct backtrace_state *state,
   stream_crc = (compressed[offset - 4]
 		| (compressed[offset - 3] << 8)
 		| (compressed[offset - 2] << 16)
-		| (compressed[offset - 1] << 24));
+		| ((unsigned)(compressed[offset - 1]) << 24));
   if (unlikely (computed_crc != stream_crc))
     {
       elf_uncompress_failed ();
@@ -3891,7 +3891,7 @@ elf_uncompress_lzma (struct backtrace_state *state,
   stream_crc = (compressed[offset]
 		| (compressed[offset + 1] << 8)
 		| (compressed[offset + 2] << 16)
-		| (compressed[offset + 3] << 24));
+		| ((unsigned)(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;