[PATCH v2] libelf: {de,}compress: ensure zlib resource cleanup

[Matthias Maennich <maennich@google.com>]

__libelf_decompress would only cleanup zlib resources via inflateEnd()
in case inflating was successful, but would leak memory if not. Fix this
by calling inflateEnd() unconditionally.

__libelf_decompress did this all the time already, but called
deflateEnd() twice. That is not a (known) issue, but can be cleaned up
by ensuring all error paths use 'return deflate_cleanup' and the success
path calls deflateEnd() only once. Note, the deflate() needs to return
Z_STREAM_END to indicate we are done. Hence change the condition.

Fixes: 272018bba1f2 ("libelf: Add elf_compress and elf_compress_gnu.")
Signed-off-by: Matthias Maennich <maennich@google.com>
---
 libelf/elf_compress.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/libelf/elf_compress.c b/libelf/elf_compress.c
index 244467b5e3ae..b1b896890ff7 100644
--- a/libelf/elf_compress.c
+++ b/libelf/elf_compress.c
@@ -115,7 +115,7 @@ __libelf_compress (Elf_Scn *scn, size_t hsize, int ei_data,
     {
       free (out_buf);
       __libelf_seterrno (ELF_E_COMPRESS_ERROR);
-      return NULL;
+      return deflate_cleanup(NULL, NULL);
     }
 
   Elf_Data cdata;
@@ -197,13 +197,13 @@ __libelf_compress (Elf_Scn *scn, size_t hsize, int ei_data,
     }
   while (flush != Z_FINISH); /* More data blocks.  */
 
-  zrc = deflateEnd (&z);
-  if (zrc != Z_OK)
+  if (zrc != Z_STREAM_END)
     {
       __libelf_seterrno (ELF_E_COMPRESS_ERROR);
       return deflate_cleanup (NULL, NULL);
     }
 
+  deflateEnd (&z);
   *new_size = used;
   return out_buf;
 }
@@ -251,16 +251,15 @@ __libelf_decompress (void *buf_in, size_t size_in, size_t size_out)
 	}
       zrc = inflateReset (&z);
     }
-  if (likely (zrc == Z_OK))
-    zrc = inflateEnd (&z);
 
   if (unlikely (zrc != Z_OK) || unlikely (z.avail_out != 0))
     {
       free (buf_out);
+      buf_out = NULL;
       __libelf_seterrno (ELF_E_DECOMPRESS_ERROR);
-      return NULL;
     }
 
+  inflateEnd(&z);
   return buf_out;
 }
 
-- 
2.25.1.696.g5e7596f4ac-goog