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Subject[PATCH 10/23] ext4: Calculate and verify checksums for htree nodes
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Calculate and verify the checksum for directory index tree (htree) node blocks.
The checksum is stored in the last 4 bytes of the htree block and requires the
dx_entry array to stop 1 dx_entry short of the end of the block.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
fs/ext4/namei.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 156 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index e62e517..064ae7c 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -188,6 +188,121 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
struct inode *inode);

+/* checksumming functions */
+static struct dx_countlimit *get_dx_countlimit(struct inode *inode,
+ struct ext4_dir_entry *dirent,
+ int *offset)
+{
+ struct ext4_dir_entry *dp;
+ struct dx_root_info *root;
+ int count_offset;
+
+ if (le16_to_cpu(dirent->rec_len) == EXT4_BLOCK_SIZE(inode->i_sb))
+ count_offset = 8;
+ else if (le16_to_cpu(dirent->rec_len) == 12) {
+ dp = (struct ext4_dir_entry *)(((void *)dirent) + 12);
+ if (le16_to_cpu(dp->rec_len) !=
+ EXT4_BLOCK_SIZE(inode->i_sb) - 12)
+ return NULL;
+ root = (struct dx_root_info *)(((void *)dp + 12));
+ if (root->reserved_zero ||
+ root->info_length != sizeof(struct dx_root_info))
+ return NULL;
+ count_offset = 32;
+ } else
+ return NULL;
+
+ if (offset)
+ *offset = count_offset;
+ return (struct dx_countlimit *)(((void *)dirent) + count_offset);
+}
+
+static __le32 ext4_dx_csum(struct inode *inode, struct ext4_dir_entry *dirent,
+ int count_offset, int count, struct dx_tail *t)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ __u32 csum, old_csum;
+ int size;
+
+ size = count_offset + (count * sizeof(struct dx_entry));
+ old_csum = t->dt_checksum;
+ t->dt_checksum = 0;
+ csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
+ csum = ext4_chksum(sbi, csum, (__u8 *)t, sizeof(struct dx_tail));
+ t->dt_checksum = old_csum;
+
+ return cpu_to_le32(csum);
+}
+
+static int ext4_dx_csum_verify(struct inode *inode,
+ struct ext4_dir_entry *dirent)
+{
+ struct dx_countlimit *c;
+ struct dx_tail *t;
+ int count_offset, limit, count;
+
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return 1;
+
+ c = get_dx_countlimit(inode, dirent, &count_offset);
+ if (!c) {
+ EXT4_ERROR_INODE(inode, "dir seems corrupt? Run e2fsck -D.");
+ return 1;
+ }
+ limit = le16_to_cpu(c->limit);
+ count = le16_to_cpu(c->count);
+ if (count_offset + (limit * sizeof(struct dx_entry)) >
+ EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
+ EXT4_ERROR_INODE(inode, "metadata_csum set but no space for "
+ "tree checksum found. Run e2fsck -D.");
+ return 1;
+ }
+ t = (struct dx_tail *)(((struct dx_entry *)c) + limit);
+
+ if (t->dt_checksum != ext4_dx_csum(inode, dirent, count_offset,
+ count, t))
+ return 0;
+ return 1;
+}
+
+static void ext4_dx_csum_set(struct inode *inode, struct ext4_dir_entry *dirent)
+{
+ struct dx_countlimit *c;
+ struct dx_tail *t;
+ int count_offset, limit, count;
+
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return;
+
+ c = get_dx_countlimit(inode, dirent, &count_offset);
+ if (!c) {
+ EXT4_ERROR_INODE(inode, "dir seems corrupt? Run e2fsck -D.");
+ return;
+ }
+ limit = le16_to_cpu(c->limit);
+ count = le16_to_cpu(c->count);
+ if (count_offset + (limit * sizeof(struct dx_entry)) >
+ EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
+ EXT4_ERROR_INODE(inode, "metadata_csum set but no space for "
+ "tree checksum. Run e2fsck -D.");
+ return;
+ }
+ t = (struct dx_tail *)(((struct dx_entry *)c) + limit);
+
+ t->dt_checksum = ext4_dx_csum(inode, dirent, count_offset, count, t);
+}
+
+static inline int ext4_handle_dirty_dx_node(handle_t *handle,
+ struct inode *inode,
+ struct buffer_head *bh)
+{
+ ext4_dx_csum_set(inode, (struct ext4_dir_entry *)bh->b_data);
+ return ext4_handle_dirty_metadata(handle, inode, bh);
+}
+
/*
* p is at least 6 bytes before the end of page
*/
@@ -247,12 +362,20 @@ static inline unsigned dx_root_limit(struct inode *dir, unsigned infosize)
{
unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(1) -
EXT4_DIR_REC_LEN(2) - infosize;
+
+ if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ entry_space -= sizeof(struct dx_tail);
return entry_space / sizeof(struct dx_entry);
}

static inline unsigned dx_node_limit(struct inode *dir)
{
unsigned entry_space = dir->i_sb->s_blocksize - EXT4_DIR_REC_LEN(0);
+
+ if (EXT4_HAS_RO_COMPAT_FEATURE(dir->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ entry_space -= sizeof(struct dx_tail);
return entry_space / sizeof(struct dx_entry);
}

@@ -398,6 +521,15 @@ dx_probe(const struct qstr *d_name, struct inode *dir,
goto fail;
}

+ if (!buffer_verified(bh) &&
+ !ext4_dx_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data)) {
+ ext4_warning(dir->i_sb, "Root failed checksum");
+ brelse(bh);
+ *err = ERR_BAD_DX_DIR;
+ goto fail;
+ }
+ set_buffer_verified(bh);
+
entries = (struct dx_entry *) (((char *)&root->info) +
root->info.info_length);

@@ -458,6 +590,17 @@ dx_probe(const struct qstr *d_name, struct inode *dir,
if (!(bh = ext4_bread (NULL,dir, dx_get_block(at), 0, err)))
goto fail2;
at = entries = ((struct dx_node *) bh->b_data)->entries;
+
+ if (!buffer_verified(bh) &&
+ !ext4_dx_csum_verify(dir,
+ (struct ext4_dir_entry *)bh->b_data)) {
+ ext4_warning(dir->i_sb, "Node failed checksum");
+ brelse(bh);
+ *err = ERR_BAD_DX_DIR;
+ goto fail;
+ }
+ set_buffer_verified(bh);
+
if (dx_get_limit(entries) != dx_node_limit (dir)) {
ext4_warning(dir->i_sb,
"dx entry: limit != node limit");
@@ -557,6 +700,15 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash,
if (!(bh = ext4_bread(NULL, dir, dx_get_block(p->at),
0, &err)))
return err; /* Failure */
+
+ if (!buffer_verified(bh) &&
+ !ext4_dx_csum_verify(dir,
+ (struct ext4_dir_entry *)bh->b_data)) {
+ ext4_warning(dir->i_sb, "Node failed checksum");
+ return -EIO;
+ }
+ set_buffer_verified(bh);
+
p++;
brelse(p->bh);
p->bh = bh;
@@ -1232,7 +1384,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
err = ext4_handle_dirty_metadata(handle, dir, bh2);
if (err)
goto journal_error;
- err = ext4_handle_dirty_metadata(handle, dir, frame->bh);
+ err = ext4_handle_dirty_dx_node(handle, dir, frame->bh);
if (err)
goto journal_error;
brelse(bh2);
@@ -1419,7 +1571,7 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,
frame->bh = bh;
bh = bh2;

- ext4_handle_dirty_metadata(handle, dir, frame->bh);
+ ext4_handle_dirty_dx_node(handle, dir, frame->bh);
ext4_handle_dirty_metadata(handle, dir, bh);

de = do_split(handle,dir, &bh, frame, &hinfo, &retval);
@@ -1594,7 +1746,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
dxtrace(dx_show_index("node", frames[1].entries));
dxtrace(dx_show_index("node",
((struct dx_node *) bh2->b_data)->entries));
- err = ext4_handle_dirty_metadata(handle, dir, bh2);
+ err = ext4_handle_dirty_dx_node(handle, dir, bh2);
if (err)
goto journal_error;
brelse (bh2);
@@ -1620,7 +1772,7 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
if (err)
goto journal_error;
}
- err = ext4_handle_dirty_metadata(handle, dir, frames[0].bh);
+ err = ext4_handle_dirty_dx_node(handle, dir, frames[0].bh);
if (err) {
ext4_std_error(inode->i_sb, err);
goto cleanup;


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