initramfs: handle unrecognised decompressor when unpacking

commit df37bd156dcb4f5441beaf5bde444adac974e9a0 upstream.

The unpack routine fails to handle the decompress_method() returning
unrecognised decompressor (compress_name == NULL).  This results in the
routine looping eventually oopsing on an out of bounds memory access.

Note this bug is usually hidden, only triggering on trailing junk after
one or more correct compressed blocks.  The case of the compressed archive
being complete junk is (by accident?) caught by the if (state != Reset)
check because state is initialised to Start, but not updated due to the
decompressor not having been called.  Obviously if the junk is trailing a
correctly decompressed buffer, state == Reset from the previous call to
the decompressor.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/init/initramfs.c b/init/initramfs.c
index 4c00edc59689034895ad6728c9b5b4505a8386b3..1fd59b81dd9a5f1f037613db4c624d56d7f4d630 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -455,7 +455,8 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len)
                                         compress_name);
                                message = msg_buf;
                        }
-               }
+               } else
+                       error("junk in compressed archive");
                if (state != Reset)
                        error("junk in compressed archive");
                this_header = saved_offset + my_inptr;