From: Jan Kara <jack@suse.cz>
Date: Wed, 11 May 2016 09:58:49 +0000 (+0200)
Subject: ext2: Avoid DAX zeroing to corrupt data
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=86b0624e42d03a424e9571b8591d191c436f9af1;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

ext2: Avoid DAX zeroing to corrupt data

Currently ext2 zeroes any data blocks allocated for DAX inode however it
still returns them as BH_New. Thus DAX code zeroes them again in
dax_insert_mapping() which can possibly overwrite the data that has been
already stored to those blocks by a racing dax_io(). Avoid marking
pre-zeroed buffers as new.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 038d0ed5f565..9a14af3b1a69 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -745,11 +745,11 @@ static int ext2_get_blocks(struct inode *inode,
 			mutex_unlock(&ei->truncate_mutex);
 			goto cleanup;
 		}
-	}
+	} else
+		set_buffer_new(bh_result);
 
 	ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
 	mutex_unlock(&ei->truncate_mutex);
-	set_buffer_new(bh_result);
 got_it:
 	map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
 	if (count > blocks_to_boundary)