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authorTheodore Ts'o <tytso@mit.edu>2016-04-30 00:48:54 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-04-30 00:48:54 -0400
commitc9eb13a9105e2e418f72e46a2b6da3f49e696902 (patch)
treef7c98c4a9720744af5957c76b483a6f1ba0e7dd8
parent8d2ae1cbe8a984d7a755755fb53955de2f60a2f9 (diff)
ext4: fix hang when processing corrupted orphaned inode list
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 Cc: stable@vger.kernel.org Reported by: Vegard Nossum <vegard.nossum@oracle.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
-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 237b877d316d..c2caf2df3695 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1183,11 +1183,13 @@ 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)