| From aeb1e5d69a5be592e86a926be73efb38c55af404 Mon Sep 17 00:00:00 2001 |
| From: Theodore Ts'o <tytso@mit.edu> |
| Date: Thu, 29 Nov 2012 21:21:22 -0500 |
| Subject: ext4: fix possible use after free with metadata csum |
| |
| From: Theodore Ts'o <tytso@mit.edu> |
| |
| commit aeb1e5d69a5be592e86a926be73efb38c55af404 upstream. |
| |
| Commit fa77dcfafeaa introduces block bitmap checksum calculation into |
| ext4_new_inode() in the case that block group was uninitialized. |
| However we brelse() the bitmap buffer before we attempt to checksum it |
| so we have no guarantee that the buffer is still there. |
| |
| Fix this by releasing the buffer after the possible checksum |
| computation. |
| |
| Signed-off-by: Lukas Czerner <lczerner@redhat.com> |
| Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> |
| Acked-by: Darrick J. Wong <darrick.wong@oracle.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/ext4/ialloc.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/fs/ext4/ialloc.c |
| +++ b/fs/ext4/ialloc.c |
| @@ -762,7 +762,6 @@ got: |
| |
| BUFFER_TRACE(block_bitmap_bh, "dirty block bitmap"); |
| err = ext4_handle_dirty_metadata(handle, NULL, block_bitmap_bh); |
| - brelse(block_bitmap_bh); |
| |
| /* recheck and clear flag under lock if we still need to */ |
| ext4_lock_group(sb, group); |
| @@ -775,6 +774,7 @@ got: |
| ext4_group_desc_csum_set(sb, group, gdp); |
| } |
| ext4_unlock_group(sb, group); |
| + brelse(block_bitmap_bh); |
| |
| if (err) |
| goto fail; |
