Commit aeb1e5d6 authored Nov 29, 2012 by Theodore Ts'o

ext4: fix possible use after free with metadata csum



Commit fa77dcfa 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>
Cc: stable@vger.kernel.org

parent 69c499d1

fs/ext4/ialloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -762,7 +762,6 @@ struct inode ext4_new_inode(handle_t handle, struct inode *dir, umode_t mode,

		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 @@ struct inode ext4_new_inode(handle_t handle, struct inode *dir, umode_t mode,
		ext4_group_desc_csum_set(sb, group, gdp);
		}
		ext4_unlock_group(sb, group);
		brelse(block_bitmap_bh);

		if (err)
		goto fail;