Squashfs: Fix oops when reading fsfuzzer corrupted filesystems

This fixes a code regression caused by the recent mainlining changes.
The recent code changes call zlib_inflate repeatedly, decompressing into
separate 4K buffers, this code didn't check for the possibility that
zlib_inflate might ask for too many buffers when decompressing corrupted
data.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

1 files changed, 11 insertions, 2 deletions

diff --git a/fs/squashfs/block.c b/fs/squashfs/block.c
index c837dfc2b3c6..321728f48f2d 100644
--- a/fs/squashfs/block.c
+++ b/fs/squashfs/block.c
@@ -80,7 +80,7 @@ static struct buffer_head *get_block_length(struct super_block *sb,
  * generated a larger block - this does occasionally happen with zlib).
  */
 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
-                        int length, u64 *next_index, int srclength)
+                        int length, u64 *next_index, int srclength, int pages)
 {
         struct squashfs_sb_info *msblk = sb->s_fs_info;
         struct buffer_head **bh;
@@ -185,6 +185,14 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
                         }
 
                         if (msblk->stream.avail_out == 0) {
+                                if (page == pages) {
+                                        ERROR("zlib_inflate tried to "
+                                                "decompress too much data, "
+                                                "expected %d bytes.  Zlib "
+                                                "data probably corrupt\n",
+                                                srclength);
+                                        goto release_mutex;
+                                }
                                 msblk->stream.next_out = buffer[page++];
                                 msblk->stream.avail_out = PAGE_CACHE_SIZE;
                         }
@@ -268,7 +276,8 @@ block_release:
                 put_bh(bh[k]);
 
 read_failure:
-        ERROR("sb_bread failed reading block 0x%llx\n", cur_index);
+        ERROR("squashfs_read_data failed to read block 0x%llx\n",
+                                        (unsigned long long) index);
         kfree(bh);
         return -EIO;
 }