Fix decompression logic.

diff --git a/libdwfl/gzip.c b/libdwfl/gzip.c
index effde5f1dc8c52dad1bcf6814a0524242a44f62a..ed602a6669535e21b2068226474ccf3fcc0a8c63 100644 (file)
--- a/libdwfl/gzip.c
+++ b/libdwfl/gzip.c
@@ -52,6 +52,7 @@
 #include <unistd.h>
 
 #ifdef BZLIB
+# define inflate_groks_header  true
 # include <bzlib.h>
 # define unzip         __libdw_bunzip2
 # define DWFL_E_ZLIB   DWFL_E_BZLIB
@@ -66,6 +67,7 @@
 # define gzread                BZ2_bzread
 # define gzclose       BZ2_bzclose
 #else
+# define inflate_groks_header  false
 # include <zlib.h>
 # define unzip         __libdw_gunzip
 # define MAGIC         "\037\213"
@@ -115,19 +117,25 @@ unzip (int fd, off64_t start_offset,
     return failure;
   }
 
-  if (mapped != NULL)
+  /* If the file is already mapped in, look at the header.  */
+  if (mapped != NULL
+      && (mapped_size <= sizeof MAGIC
+         || memcmp (mapped, MAGIC, sizeof MAGIC - 1)))
+    /* Not a compressed file.  */
+    return DWFL_E_BADELF;
+
+  if (mapped != NULL && inflate_groks_header)
     {
-      /* The file is already mapped in.  Look at the header.  */
-      if (mapped_size <= sizeof MAGIC || memcmp (mapped, MAGIC, sizeof MAGIC))
-       /* Not a compressed file.  */
-       return DWFL_E_CB;
+      /* This style actually only works with bzlib.
+        The stupid zlib interface has nothing to grok the
+        gzip file headers except the slow gzFile interface.  */
 
       z_stream z = { .next_in = mapped, .avail_in = mapped_size };
       int result = inflateInit (&z);
       if (result != Z (OK))
        return zlib_fail (result);
 
-      while ((result = inflate (&z, Z_SYNC_FLUSH)) == Z (OK))
+      do
        {
          ptrdiff_t pos = (void *) z.next_out - buffer;
          if (!bigger_buffer (z.avail_in))
@@ -138,6 +146,7 @@ unzip (int fd, off64_t start_offset,
          z.next_out = buffer + pos;
          z.avail_out = size - pos;
        }
+      while ((result = inflate (&z, Z_SYNC_FLUSH)) == Z (OK));
 
 #ifdef BZLIB
       uint64_t total_out = (((uint64_t) z.total_out_hi32 << 32)
@@ -154,16 +163,18 @@ unzip (int fd, off64_t start_offset,
     }
   else
     {
+      /* Let the decompression library read the file directly.  */
+
       int d = dup (fd);
       if (unlikely (d < 0))
-       return DWFL_E_CB;
+       return DWFL_E_BADELF;
       if (start_offset != 0)
        {
          off64_t off = lseek (d, start_offset, SEEK_SET);
          if (off != start_offset)
            {
              close (d);
-             return DWFL_E_CB;
+             return DWFL_E_BADELF;
            }
        }
       gzFile zf = gzdopen (d, "r");
@@ -179,7 +190,7 @@ unzip (int fd, off64_t start_offset,
       if (gzdirect (zf))
        {
          gzclose (zf);
-         return DWFL_E_CB;
+         return DWFL_E_BADELF;
        }
 #endif
 
@@ -201,7 +212,7 @@ unzip (int fd, off64_t start_offset,
                {
                  gzclose (zf);
                  free (buffer);
-                 return DWFL_E_CB;
+                 return DWFL_E_BADELF;
                }
 #endif
              gzclose (zf);
@@ -219,5 +230,5 @@ unzip (int fd, off64_t start_offset,
   *whole = buffer;
   *whole_size = size;
 
-return DWFL_E_NOERROR;
+  return DWFL_E_NOERROR;
 }