ext4: avoid modifying checksum fields directly during checksum verification

[deliverable/linux.git] / fs / ext4 / xattr.c

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index e79bd32b9b798735f312ba87e3658e0796c44a2a..39e9cfb1b3715c2fcf2b81c0e03c2183d58c9100 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -121,17 +121,18 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
 {
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        __u32 csum;
-       __le32 save_csum;
        __le64 dsk_block_nr = cpu_to_le64(block_nr);
+       __u32 dummy_csum = 0;
+       int offset = offsetof(struct ext4_xattr_header, h_checksum);
 
-       save_csum = hdr->h_checksum;
-       hdr->h_checksum = 0;
        csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&dsk_block_nr,
                           sizeof(dsk_block_nr));
-       csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
-                          EXT4_BLOCK_SIZE(inode->i_sb));
+       csum = ext4_chksum(sbi, csum, (__u8 *)hdr, offset);
+       csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, sizeof(dummy_csum));
+       offset += sizeof(dummy_csum);
+       csum = ext4_chksum(sbi, csum, (__u8 *)hdr + offset,
+                          EXT4_BLOCK_SIZE(inode->i_sb) - offset);
 
-       hdr->h_checksum = save_csum;
        return cpu_to_le32(csum);
 }