From: Jan Kara Date: Mon, 16 Jun 2014 03:46:28 +0000 (-0400) Subject: ext4: Fix buffer double free in ext4_alloc_branch() X-Git-Tag: upstream/snapshot3+hdmi~2162 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cbbe137036cec32f997d9dc945b45412a92bad61;hp=baa9dbe85a5ce7d415837652a14c2edac0455880;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git ext4: Fix buffer double free in ext4_alloc_branch() commit c5c7b8ddfbf8cb3b2291e515a34ab1b8982f5a2d upstream. 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 Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index 594009f..3b91d24 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],