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authorTheodore Ts'o <tytso@mit.edu>2016-04-30 00:48:54 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-06-07 17:21:59 -0700
commitd537a94dbb33f5b14386c933b7f9d52e445f0462 (patch)
tree03b5da051e85d6f318d3c015c686b75f96e33bfe
parent4bb87c0487e7b7c009d195310f8aeda63d61e2c5 (diff)
downloadlwn-d537a94dbb33f5b14386c933b7f9d52e445f0462.tar.gz
lwn-d537a94dbb33f5b14386c933b7f9d52e445f0462.zip
ext4: fix hang when processing corrupted orphaned inode list
commit c9eb13a9105e2e418f72e46a2b6da3f49e696902 upstream. If the orphaned inode list contains inode #5, ext4_iget() returns a bad inode (since the bootloader inode should never be referenced directly). Because of the bad inode, we end up processing the inode repeatedly and this hangs the machine. This can be reproduced via: mke2fs -t ext4 /tmp/foo.img 100 debugfs -w -R "ssv last_orphan 5" /tmp/foo.img mount -o loop /tmp/foo.img /mnt (But don't do this if you are using an unpatched kernel if you care about the system staying functional. :-) This bug was found by the port of American Fuzzy Lop into the kernel to find file system problems[1]. (Since it *only* happens if inode #5 shows up on the orphan list --- 3, 7, 8, etc. won't do it, it's not surprising that AFL needed two hours before it found it.) [1] http://events.linuxfoundation.org/sites/events/files/slides/AFL%20filesystem%20fuzzing%2C%20Vault%202016_0.pdf Reported by: Vegard Nossum <vegard.nossum@oracle.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/ext4/ialloc.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index a8d1a64d8cb0..4920cbdd47cc 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1097,11 +1097,13 @@ struct inode *ext4_orphan_get(struct super_block *sb, unsigned long ino)
goto iget_failed;
/*
- * If the orphans has i_nlinks > 0 then it should be able to be
- * truncated, otherwise it won't be removed from the orphan list
- * during processing and an infinite loop will result.
+ * If the orphans has i_nlinks > 0 then it should be able to
+ * be truncated, otherwise it won't be removed from the orphan
+ * list during processing and an infinite loop will result.
+ * Similarly, it must not be a bad inode.
*/
- if (inode->i_nlink && !ext4_can_truncate(inode))
+ if ((inode->i_nlink && !ext4_can_truncate(inode)) ||
+ is_bad_inode(inode))
goto bad_orphan;
if (NEXT_ORPHAN(inode) > max_ino)