ext4: calculate and verify checksums of directory leaf blocks

Calculate and verify the checksums for directory leaf blocks
(i.e. blocks that only contain actual directory entries).  The
checksum lives in what looks to be an unused directory entry with a 0
name_len at the end of the block.  This scheme is not used for
internal htree nodes because the mechanism in place there only costs
one dx_entry, whereas the "empty" directory entry would cost two
dx_entries.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 245 insertions, 15 deletions

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index f8efedde7593..5861d64929f6 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -189,6 +189,115 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
                              struct inode *inode);
 
 /* checksumming functions */
+#define EXT4_DIRENT_TAIL(block, blocksize) \
+        ((struct ext4_dir_entry_tail *)(((void *)(block)) + \
+                                        ((blocksize) - \
+                                         sizeof(struct ext4_dir_entry_tail))))
+
+static void initialize_dirent_tail(struct ext4_dir_entry_tail *t,
+                                   unsigned int blocksize)
+{
+        memset(t, 0, sizeof(struct ext4_dir_entry_tail));
+        t->det_rec_len = ext4_rec_len_to_disk(
+                        sizeof(struct ext4_dir_entry_tail), blocksize);
+        t->det_reserved_ft = EXT4_FT_DIR_CSUM;
+}
+
+/* Walk through a dirent block to find a checksum "dirent" at the tail */
+static struct ext4_dir_entry_tail *get_dirent_tail(struct inode *inode,
+                                                   struct ext4_dir_entry *de)
+{
+        struct ext4_dir_entry_tail *t;
+
+#ifdef PARANOID
+        struct ext4_dir_entry *d, *top;
+
+        d = de;
+        top = (struct ext4_dir_entry *)(((void *)de) +
+                (EXT4_BLOCK_SIZE(inode->i_sb) -
+                sizeof(struct ext4_dir_entry_tail)));
+        while (d < top && d->rec_len)
+                d = (struct ext4_dir_entry *)(((void *)d) +
+                    le16_to_cpu(d->rec_len));
+
+        if (d != top)
+                return NULL;
+
+        t = (struct ext4_dir_entry_tail *)d;
+#else
+        t = EXT4_DIRENT_TAIL(de, EXT4_BLOCK_SIZE(inode->i_sb));
+#endif
+
+        if (t->det_reserved_zero1 ||
+            le16_to_cpu(t->det_rec_len) != sizeof(struct ext4_dir_entry_tail) ||
+            t->det_reserved_zero2 ||
+            t->det_reserved_ft != EXT4_FT_DIR_CSUM)
+                return NULL;
+
+        return t;
+}
+
+static __le32 ext4_dirent_csum(struct inode *inode,
+                               struct ext4_dir_entry *dirent, int size)
+{
+        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        __u32 csum;
+
+        csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
+        return cpu_to_le32(csum);
+}
+
+int ext4_dirent_csum_verify(struct inode *inode, struct ext4_dir_entry *dirent)
+{
+        struct ext4_dir_entry_tail *t;
+
+        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                return 1;
+
+        t = get_dirent_tail(inode, dirent);
+        if (!t) {
+                EXT4_ERROR_INODE(inode, "metadata_csum set but no space in dir "
+                                 "leaf for checksum.  Please run e2fsck -D.");
+                return 0;
+        }
+
+        if (t->det_checksum != ext4_dirent_csum(inode, dirent,
+                                                (void *)t - (void *)dirent))
+                return 0;
+
+        return 1;
+}
+
+static void ext4_dirent_csum_set(struct inode *inode,
+                                 struct ext4_dir_entry *dirent)
+{
+        struct ext4_dir_entry_tail *t;
+
+        if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+                                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                return;
+
+        t = get_dirent_tail(inode, dirent);
+        if (!t) {
+                EXT4_ERROR_INODE(inode, "metadata_csum set but no space in dir "
+                                 "leaf for checksum.  Please run e2fsck -D.");
+                return;
+        }
+
+        t->det_checksum = ext4_dirent_csum(inode, dirent,
+                                           (void *)t - (void *)dirent);
+}
+
+static inline int ext4_handle_dirty_dirent_node(handle_t *handle,
+                                                struct inode *inode,
+                                                struct buffer_head *bh)
+{
+        ext4_dirent_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
+        return ext4_handle_dirty_metadata(handle, inode, bh);
+}
+
 static struct dx_countlimit *get_dx_countlimit(struct inode *inode,
                                                struct ext4_dir_entry *dirent,
                                                int *offset)
@@ -737,6 +846,11 @@ static int htree_dirblock_to_tree(struct file *dir_file,
         if (!(bh = ext4_bread (NULL, dir, block, 0, &err)))
                 return err;
 
+        if (!buffer_verified(bh) &&
+            !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))
+                return -EIO;
+        set_buffer_verified(bh);
+
         de = (struct ext4_dir_entry_2 *) bh->b_data;
         top = (struct ext4_dir_entry_2 *) ((char *) de +
                                            dir->i_sb->s_blocksize -
@@ -1096,6 +1210,15 @@ restart:
                         brelse(bh);
                         goto next;
                 }
+                if (!buffer_verified(bh) &&
+                    !ext4_dirent_csum_verify(dir,
+                                (struct ext4_dir_entry *)bh->b_data)) {
+                        EXT4_ERROR_INODE(dir, "checksumming directory "
+                                         "block %lu", (unsigned long)block);
+                        brelse(bh);
+                        goto next;
+                }
+                set_buffer_verified(bh);
                 i = search_dirblock(bh, dir, d_name,
                             block << EXT4_BLOCK_SIZE_BITS(sb), res_dir);
                 if (i == 1) {
@@ -1147,6 +1270,16 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct q
                 if (!(bh = ext4_bread(NULL, dir, block, 0, err)))
                         goto errout;
 
+                if (!buffer_verified(bh) &&
+                    !ext4_dirent_csum_verify(dir,
+                                (struct ext4_dir_entry *)bh->b_data)) {
+                        EXT4_ERROR_INODE(dir, "checksumming directory "
+                                         "block %lu", (unsigned long)block);
+                        brelse(bh);
+                        *err = -EIO;
+                        goto errout;
+                }
+                set_buffer_verified(bh);
                 retval = search_dirblock(bh, dir, d_name,
                                          block << EXT4_BLOCK_SIZE_BITS(sb),
                                          res_dir);
@@ -1319,8 +1452,14 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
         char *data1 = (*bh)->b_data, *data2;
         unsigned split, move, size;
         struct ext4_dir_entry_2 *de = NULL, *de2;
+        struct ext4_dir_entry_tail *t;
+        int     csum_size = 0;
         int     err = 0, i;
 
+        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
+
         bh2 = ext4_append (handle, dir, &newblock, &err);
         if (!(bh2)) {
                 brelse(*bh);
@@ -1367,10 +1506,20 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
         /* Fancy dance to stay within two buffers */
         de2 = dx_move_dirents(data1, data2, map + split, count - split, blocksize);
         de = dx_pack_dirents(data1, blocksize);
-        de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de,
+        de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
+                                           (char *) de,
                                            blocksize);
-        de2->rec_len = ext4_rec_len_to_disk(data2 + blocksize - (char *) de2,
+        de2->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -
+                                            (char *) de2,
                                             blocksize);
+        if (csum_size) {
+                t = EXT4_DIRENT_TAIL(data2, blocksize);
+                initialize_dirent_tail(t, blocksize);
+
+                t = EXT4_DIRENT_TAIL(data1, blocksize);
+                initialize_dirent_tail(t, blocksize);
+        }
+
         dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data1, blocksize, 1));
         dxtrace(dx_show_leaf (hinfo, (struct ext4_dir_entry_2 *) data2, blocksize, 1));
 
@@ -1381,7 +1530,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
                 de = de2;
         }
         dx_insert_block(frame, hash2 + continued, newblock);
-        err = ext4_handle_dirty_metadata(handle, dir, bh2);
+        err = ext4_handle_dirty_dirent_node(handle, dir, bh2);
         if (err)
                 goto journal_error;
         err = ext4_handle_dirty_dx_node(handle, dir, frame->bh);
@@ -1421,11 +1570,16 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
         unsigned short  reclen;
         int             nlen, rlen, err;
         char            *top;
+        int             csum_size = 0;
+
+        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
 
         reclen = EXT4_DIR_REC_LEN(namelen);
         if (!de) {
                 de = (struct ext4_dir_entry_2 *)bh->b_data;
-                top = bh->b_data + blocksize - reclen;
+                top = bh->b_data + (blocksize - csum_size) - reclen;
                 while ((char *) de <= top) {
                         if (ext4_check_dir_entry(dir, NULL, de, bh, offset))
                                 return -EIO;
@@ -1481,7 +1635,7 @@ static int add_dirent_to_buf(handle_t *handle, struct dentry *dentry,
         dir->i_version++;
         ext4_mark_inode_dirty(handle, dir);
         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
-        err = ext4_handle_dirty_metadata(handle, dir, bh);
+        err = ext4_handle_dirty_dirent_node(handle, dir, bh);
         if (err)
                 ext4_std_error(dir->i_sb, err);
         return 0;
@@ -1502,6 +1656,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
         struct dx_frame frames[2], *frame;
         struct dx_entry *entries;
         struct ext4_dir_entry_2 *de, *de2;
+        struct ext4_dir_entry_tail *t;
         char            *data1, *top;
         unsigned        len;
         int             retval;
@@ -1509,6 +1664,11 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
         struct dx_hash_info hinfo;
         ext4_lblk_t  block;
         struct fake_dirent *fde;
+        int             csum_size = 0;
+
+        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
 
         blocksize =  dir->i_sb->s_blocksize;
         dxtrace(printk(KERN_DEBUG "Creating index: inode %lu\n", dir->i_ino));
@@ -1529,7 +1689,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
                 brelse(bh);
                 return -EIO;
         }
-        len = ((char *) root) + blocksize - (char *) de;
+        len = ((char *) root) + (blocksize - csum_size) - (char *) de;
 
         /* Allocate new block for the 0th block's dirents */
         bh2 = ext4_append(handle, dir, &block, &retval);
@@ -1545,8 +1705,15 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
         top = data1 + len;
         while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top)
                 de = de2;
-        de->rec_len = ext4_rec_len_to_disk(data1 + blocksize - (char *) de,
+        de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
+                                           (char *) de,
                                            blocksize);
+
+        if (csum_size) {
+                t = EXT4_DIRENT_TAIL(data1, blocksize);
+                initialize_dirent_tail(t, blocksize);
+        }
+
         /* Initialize the root; the dot dirents already exist */
         de = (struct ext4_dir_entry_2 *) (&root->dotdot);
         de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(2),
@@ -1572,7 +1739,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
         bh = bh2;
 
         ext4_handle_dirty_dx_node(handle, dir, frame->bh);
-        ext4_handle_dirty_metadata(handle, dir, bh);
+        ext4_handle_dirty_dirent_node(handle, dir, bh);
 
         de = do_split(handle,dir, &bh, frame, &hinfo, &retval);
         if (!de) {
@@ -1608,11 +1775,17 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
         struct inode *dir = dentry->d_parent->d_inode;
         struct buffer_head *bh;
         struct ext4_dir_entry_2 *de;
+        struct ext4_dir_entry_tail *t;
         struct super_block *sb;
         int     retval;
         int     dx_fallback=0;
         unsigned blocksize;
         ext4_lblk_t block, blocks;
+        int     csum_size = 0;
+
+        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
 
         sb = dir->i_sb;
         blocksize = sb->s_blocksize;
@@ -1631,6 +1804,11 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
                 bh = ext4_bread(handle, dir, block, 0, &retval);
                 if(!bh)
                         return retval;
+                if (!buffer_verified(bh) &&
+                    !ext4_dirent_csum_verify(dir,
+                                (struct ext4_dir_entry *)bh->b_data))
+                        return -EIO;
+                set_buffer_verified(bh);
                 retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
                 if (retval != -ENOSPC) {
                         brelse(bh);
@@ -1647,7 +1825,13 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
                 return retval;
         de = (struct ext4_dir_entry_2 *) bh->b_data;
         de->inode = 0;
-        de->rec_len = ext4_rec_len_to_disk(blocksize, blocksize);
+        de->rec_len = ext4_rec_len_to_disk(blocksize - csum_size, blocksize);
+
+        if (csum_size) {
+                t = EXT4_DIRENT_TAIL(bh->b_data, blocksize);
+                initialize_dirent_tail(t, blocksize);
+        }
+
         retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
         brelse(bh);
         if (retval == 0)
@@ -1679,6 +1863,11 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
         if (!(bh = ext4_bread(handle,dir, dx_get_block(frame->at), 0, &err)))
                 goto cleanup;
 
+        if (!buffer_verified(bh) &&
+            !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))
+                goto journal_error;
+        set_buffer_verified(bh);
+
         BUFFER_TRACE(bh, "get_write_access");
         err = ext4_journal_get_write_access(handle, bh);
         if (err)
@@ -1804,12 +1993,17 @@ static int ext4_delete_entry(handle_t *handle,
 {
         struct ext4_dir_entry_2 *de, *pde;
         unsigned int blocksize = dir->i_sb->s_blocksize;
+        int csum_size = 0;
         int i, err;
 
+        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
+
         i = 0;
         pde = NULL;
         de = (struct ext4_dir_entry_2 *) bh->b_data;
-        while (i < bh->b_size) {
+        while (i < bh->b_size - csum_size) {
                 if (ext4_check_dir_entry(dir, NULL, de, bh, i))
                         return -EIO;
                 if (de == de_del)  {
@@ -1830,7 +2024,7 @@ static int ext4_delete_entry(handle_t *handle,
                                 de->inode = 0;
                         dir->i_version++;
                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
-                        err = ext4_handle_dirty_metadata(handle, dir, bh);
+                        err = ext4_handle_dirty_dirent_node(handle, dir, bh);
                         if (unlikely(err)) {
                                 ext4_std_error(dir->i_sb, err);
                                 return err;
@@ -1972,9 +2166,15 @@ static int ext4_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
         struct inode *inode;
         struct buffer_head *dir_block = NULL;
         struct ext4_dir_entry_2 *de;
+        struct ext4_dir_entry_tail *t;
         unsigned int blocksize = dir->i_sb->s_blocksize;
+        int csum_size = 0;
         int err, retries = 0;
 
+        if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                csum_size = sizeof(struct ext4_dir_entry_tail);
+
         if (EXT4_DIR_LINK_MAX(dir))
                 return -EMLINK;
 
@@ -2015,16 +2215,24 @@ retry:
         ext4_set_de_type(dir->i_sb, de, S_IFDIR);
         de = ext4_next_entry(de, blocksize);
         de->inode = cpu_to_le32(dir->i_ino);
-        de->rec_len = ext4_rec_len_to_disk(blocksize - EXT4_DIR_REC_LEN(1),
+        de->rec_len = ext4_rec_len_to_disk(blocksize -
+                                           (csum_size + EXT4_DIR_REC_LEN(1)),
                                            blocksize);
         de->name_len = 2;
         strcpy(de->name, "..");
         ext4_set_de_type(dir->i_sb, de, S_IFDIR);
         set_nlink(inode, 2);
+
+        if (csum_size) {
+                t = EXT4_DIRENT_TAIL(dir_block->b_data, blocksize);
+                initialize_dirent_tail(t, blocksize);
+        }
+
         BUFFER_TRACE(dir_block, "call ext4_handle_dirty_metadata");
-        err = ext4_handle_dirty_metadata(handle, inode, dir_block);
+        err = ext4_handle_dirty_dirent_node(handle, inode, dir_block);
         if (err)
                 goto out_clear_inode;
+        set_buffer_verified(dir_block);
         err = ext4_mark_inode_dirty(handle, inode);
         if (!err)
                 err = ext4_add_entry(handle, dentry, inode);
@@ -2074,6 +2282,14 @@ static int empty_dir(struct inode *inode)
                                      inode->i_ino);
                 return 1;
         }
+        if (!buffer_verified(bh) &&
+            !ext4_dirent_csum_verify(inode,
+                        (struct ext4_dir_entry *)bh->b_data)) {
+                EXT4_ERROR_INODE(inode, "checksum error reading directory "
+                                 "lblock 0");
+                return -EIO;
+        }
+        set_buffer_verified(bh);
         de = (struct ext4_dir_entry_2 *) bh->b_data;
         de1 = ext4_next_entry(de, sb->s_blocksize);
         if (le32_to_cpu(de->inode) != inode->i_ino ||
@@ -2105,6 +2321,14 @@ static int empty_dir(struct inode *inode)
                                 offset += sb->s_blocksize;
                                 continue;
                         }
+                        if (!buffer_verified(bh) &&
+                            !ext4_dirent_csum_verify(inode,
+                                        (struct ext4_dir_entry *)bh->b_data)) {
+                                EXT4_ERROR_INODE(inode, "checksum error "
+                                                 "reading directory lblock 0");
+                                return -EIO;
+                        }
+                        set_buffer_verified(bh);
                         de = (struct ext4_dir_entry_2 *) bh->b_data;
                 }
                 if (ext4_check_dir_entry(inode, NULL, de, bh, offset)) {
@@ -2605,6 +2829,11 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
                 dir_bh = ext4_bread(handle, old_inode, 0, 0, &retval);
                 if (!dir_bh)
                         goto end_rename;
+                if (!buffer_verified(dir_bh) &&
+                    !ext4_dirent_csum_verify(old_inode,
+                                (struct ext4_dir_entry *)dir_bh->b_data))
+                        goto end_rename;
+                set_buffer_verified(dir_bh);
                 if (le32_to_cpu(PARENT_INO(dir_bh->b_data,
                                 old_dir->i_sb->s_blocksize)) != old_dir->i_ino)
                         goto end_rename;
@@ -2635,7 +2864,7 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
                                         ext4_current_time(new_dir);
                 ext4_mark_inode_dirty(handle, new_dir);
                 BUFFER_TRACE(new_bh, "call ext4_handle_dirty_metadata");
-                retval = ext4_handle_dirty_metadata(handle, new_dir, new_bh);
+                retval = ext4_handle_dirty_dirent_node(handle, new_dir, new_bh);
                 if (unlikely(retval)) {
                         ext4_std_error(new_dir->i_sb, retval);
                         goto end_rename;
@@ -2689,7 +2918,8 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
                 PARENT_INO(dir_bh->b_data, new_dir->i_sb->s_blocksize) =
                                                 cpu_to_le32(new_dir->i_ino);
                 BUFFER_TRACE(dir_bh, "call ext4_handle_dirty_metadata");
-                retval = ext4_handle_dirty_metadata(handle, old_inode, dir_bh);
+                retval = ext4_handle_dirty_dirent_node(handle, old_inode,
+                                                       dir_bh);
                 if (retval) {
                         ext4_std_error(old_dir->i_sb, retval);
                         goto end_rename;