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authorJan Kara <jack@suse.cz>2014-06-15 23:46:28 -0400
committerTheodore Ts'o <tytso@mit.edu>2014-06-15 23:46:28 -0400
commitc5c7b8ddfbf8cb3b2291e515a34ab1b8982f5a2d (patch)
tree2969953563a5ed1d21570be8a9496c10f7bdcfde
parent7171511eaec5bf23fb06078f59784a3a0626b38f (diff)
ext4: Fix buffer double free in ext4_alloc_branch()
Error recovery in ext4_alloc_branch() calls ext4_forget() even for buffer corresponding to indirect block it did not allocate. This leads to brelse() being called twice for that buffer (once from ext4_forget() and once from cleanup in ext4_ind_map_blocks()) leading to buffer use count misaccounting. Eventually (but often much later because there are other users of the buffer) we will see messages like: VFS: brelse: Trying to free free buffer Another manifestation of this problem is an error: JBD2 unexpected failure: jbd2_journal_revoke: !buffer_revoked(bh); inconsistent data on disk The fix is easy - don't forget buffer we did not allocate. Also add an explanatory comment because the indexing at ext4_alloc_branch() is somewhat subtle. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
-rw-r--r--fs/ext4/indirect.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 8a57e9fcd1b9..f85bafd474dc 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -389,7 +389,13 @@ static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
return 0;
failed:
for (; i >= 0; i--) {
- if (i != indirect_blks && branch[i].bh)
+ /*
+ * We want to ext4_forget() only freshly allocated indirect
+ * blocks. Buffer for new_blocks[i-1] is at branch[i].bh and
+ * buffer at branch[0].bh is indirect block / inode already
+ * existing before ext4_alloc_branch() was called.
+ */
+ if (i > 0 && i != indirect_blks && branch[i].bh)
ext4_forget(handle, 1, inode, branch[i].bh,
branch[i].bh->b_blocknr);
ext4_free_blocks(handle, inode, NULL, new_blocks[i],