ext2: Fix fs corruption in ext2_get_xip_mem()

commit 7ba3ec5749ddb61f79f7be17b5fd7720eebc52de upstream.

Commit 8e3dffc651cb "Ext2: mark inode dirty after the function
dquot_free_block_nodirty is called" unveiled a bug in __ext2_get_block()
called from ext2_get_xip_mem(). That function called ext2_get_block()
mistakenly asking it to map 0 blocks while 1 was intended. Before the
above mentioned commit things worked out fine by luck but after that commit
we started returning that we allocated 0 blocks while we in fact
allocated 1 block and thus allocation was looping until all blocks in
the filesystem were exhausted.

Fix the problem by properly asking for one block and also add assertion
in ext2_get_blocks() to catch similar problems.

Reported-and-tested-by: Andiry Xu <andiry.xu@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 91a6945..5a45b8f 100644 (file)
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -619,6 +619,8 @@ static int ext2_get_blocks(struct inode *inode,
        int count = 0;
        ext2_fsblk_t first_block = 0;
 
+       BUG_ON(maxblocks == 0);
+
        depth = ext2_block_to_path(inode,iblock,offsets,&blocks_to_boundary);
 
        if (depth == 0)

diff --cc fs/ext2/xip.c
Simple merge