Commit cbbe137036cec32f997d9dc945b45412a92bad61
Committed by
Greg Kroah-Hartman
1 parent
baa9dbe85a
Exists in
ti-linux-3.14.y
and in
2 other branches
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 <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Showing 1 changed file with 7 additions and 1 deletions Side-by-side Diff
fs/ext4/indirect.c
... | ... | @@ -389,7 +389,13 @@ |
389 | 389 | return 0; |
390 | 390 | failed: |
391 | 391 | for (; i >= 0; i--) { |
392 | - if (i != indirect_blks && branch[i].bh) | |
392 | + /* | |
393 | + * We want to ext4_forget() only freshly allocated indirect | |
394 | + * blocks. Buffer for new_blocks[i-1] is at branch[i].bh and | |
395 | + * buffer at branch[0].bh is indirect block / inode already | |
396 | + * existing before ext4_alloc_branch() was called. | |
397 | + */ | |
398 | + if (i > 0 && i != indirect_blks && branch[i].bh) | |
393 | 399 | ext4_forget(handle, 1, inode, branch[i].bh, |
394 | 400 | branch[i].bh->b_blocknr); |
395 | 401 | ext4_free_blocks(handle, inode, NULL, new_blocks[i], |