ext4: avoid modifying checksum fields directly during checksum verification

[firefly-linux-kernel-4.4.55.git] / fs / ext4 / super.c

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 60707c9ece364ccf3c2eddfdb953d6e0868f2db6..5bab28caa9d4a882f1da662f8efb145e88cf1a09 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2030,23 +2030,25 @@ failed:
 static __le16 ext4_group_desc_csum(struct super_block *sb, __u32 block_group,
                                   struct ext4_group_desc *gdp)
 {
-       int offset;
+       int offset = offsetof(struct ext4_group_desc, bg_checksum);
        __u16 crc = 0;
        __le32 le_group = cpu_to_le32(block_group);
        struct ext4_sb_info *sbi = EXT4_SB(sb);
 
        if (ext4_has_metadata_csum(sbi->s_sb)) {
                /* Use new metadata_csum algorithm */
-               __le16 save_csum;
                __u32 csum32;
+               __u16 dummy_csum = 0;
 
-               save_csum = gdp->bg_checksum;
-               gdp->bg_checksum = 0;
                csum32 = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&le_group,
                                     sizeof(le_group));
-               csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp,
-                                    sbi->s_desc_size);
-               gdp->bg_checksum = save_csum;
+               csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp, offset);
+               csum32 = ext4_chksum(sbi, csum32, (__u8 *)&dummy_csum,
+                                    sizeof(dummy_csum));
+               offset += sizeof(dummy_csum);
+               if (offset < sbi->s_desc_size)
+                       csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp + offset,
+                                            sbi->s_desc_size - offset);
 
                crc = csum32 & 0xFFFF;
                goto out;
@@ -2056,8 +2058,6 @@ static __le16 ext4_group_desc_csum(struct super_block *sb, __u32 block_group,
        if (!ext4_has_feature_gdt_csum(sb))
                return 0;
 
-       offset = offsetof(struct ext4_group_desc, bg_checksum);
-
        crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
        crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
        crc = crc16(crc, (__u8 *)gdp, offset);