From: Theodore Ts'o Date: Fri, 30 Nov 2012 02:21:22 +0000 (-0500) Subject: ext4: fix possible use after free with metadata csum X-Git-Tag: v3.8-rc2~9^2~41 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=aeb1e5d69a5be592e86a926be73efb38c55af404;p=profile%2Fivi%2Fkernel-adaptation-intel-automotive.git ext4: fix possible use after free with metadata csum 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 Cc: stable@vger.kernel.org --- diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 3a100e7..c7efa88 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;