From 5ec1cdca458496eb8e8461738b53fcbc2d024650 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Thu, 29 Nov 2012 21:21:22 -0500 Subject: ext4: fix possible use after free with metadata csum 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 Signed-off-by: "Theodore Ts'o" Acked-by: Darrick J. Wong Signed-off-by: Greg Kroah-Hartman --- fs/ext4/ialloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 3a100e7a62a8..c7efa88d7149 100644 --- 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; -- cgit v1.2.3