To verify that a xattr entry is not pointing to the wrong xattr inode,
we currently check that the target inode has EXT4_EA_INODE_FL flag set and
also the entry size matches the target inode size.
For stronger validation, also incorporate crc32c hash of the value into
the e_hash field. This is done regardless of whether the entry lives in
the inode body or external attribute block.
Signed-off-by: Tahsin Erdogan <tah...@google.com>
---
fs/ext4/xattr.c | 106 +++++++++++++++++++++++++++++++++++---------------------
1 file changed, 67 insertions(+), 39 deletions(-)
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 6c6dce2f874e..7e9134fb4bb8 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -77,8 +77,8 @@ static void ext4_xattr_block_cache_insert(struct mb_cache *,
static struct buffer_head *
ext4_xattr_block_cache_find(struct inode *, struct ext4_xattr_header *,
struct mb_cache_entry **);
-static void ext4_xattr_hash_entry(struct ext4_xattr_entry *entry,
- void *value_base);
+static __le32 ext4_xattr_hash_entry(char *name, size_t name_len, __le32 *value,
+ size_t value_count);
static void ext4_xattr_rehash(struct ext4_xattr_header *);
static const struct xattr_handler * const ext4_xattr_handler_map[] = {
@@ -389,18 +389,20 @@ static int ext4_xattr_inode_iget(struct inode *parent,
unsigned long ea_ino,
}
/*
- * Read the value from the EA inode.
+ * Read xattr value from the EA inode.
*/
static int
-ext4_xattr_inode_get(struct inode *inode, unsigned long ea_ino, void *buffer,
- size_t size)
+ext4_xattr_inode_get(struct inode *inode, struct ext4_xattr_entry *entry,
+ void *buffer, size_t size)
{
struct mb_cache *ea_inode_cache = EA_INODE_CACHE(inode);
struct inode *ea_inode;
+ __le32 calc_e_hash, tmp_data;
u32 hash;
int err;
- err = ext4_xattr_inode_iget(inode, ea_ino, &ea_inode);
+ err = ext4_xattr_inode_iget(inode, le32_to_cpu(entry->e_value_inum),
+ &ea_inode);
if (err) {
ea_inode = NULL;
goto out;
@@ -415,11 +417,25 @@ ext4_xattr_inode_get(struct inode *inode, unsigned long
ea_ino, void *buffer,
}
err = ext4_xattr_inode_read(ea_inode, buffer, size);
- if (!err) {
- hash = ext4_xattr_inode_get_hash(ea_inode);
- mb_cache_entry_create(ea_inode_cache, GFP_NOFS, hash,
- ea_inode->i_ino, true /* reusable */);
+ if (err)
+ goto out;
+
+ hash = ext4_xattr_inode_get_hash(ea_inode);
+
+ /* Verify e_hash. */
+ tmp_data = cpu_to_le32(hash);
+ calc_e_hash = ext4_xattr_hash_entry(entry->e_name, entry->e_name_len,
+ &tmp_data, 1);
+ if (calc_e_hash != entry->e_hash) {
+ ext4_warning_inode(inode,
+ "Entry calc_e_hash=%#x does not match e_hash=%#x",
+ le32_to_cpu(calc_e_hash), le32_to_cpu(entry->e_hash));
+ err = -EFSCORRUPTED;
+ goto out;
}
+
+ mb_cache_entry_create(ea_inode_cache, GFP_NOFS, hash, ea_inode->i_ino,
+ true /* reusable */);
out:
iput(ea_inode);
return err;
@@ -465,9 +481,8 @@ ext4_xattr_block_get(struct inode *inode, int name_index,
const char *name,
if (size > buffer_size)
goto cleanup;
if (entry->e_value_inum) {
- error = ext4_xattr_inode_get(inode,
- le32_to_cpu(entry->e_value_inum),
- buffer, size);
+ error = ext4_xattr_inode_get(inode, entry, buffer,
+ size);
if (error)
goto cleanup;
} else {
@@ -515,9 +530,8 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index,
const char *name,
if (size > buffer_size)
goto cleanup;
if (entry->e_value_inum) {
- error = ext4_xattr_inode_get(inode,
- le32_to_cpu(entry->e_value_inum),
- buffer, size);
+ error = ext4_xattr_inode_get(inode, entry, buffer,
+ size);
if (error)
goto cleanup;
} else {
@@ -1634,12 +1648,36 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info
*i,
here->e_value_size = cpu_to_le32(i->value_len);
}
- if (is_block) {
- if (s->not_found || i->value)
- ext4_xattr_hash_entry(here, s->base);
- ext4_xattr_rehash((struct ext4_xattr_header *)s->base);
+ if (i->value) {
+ __le32 hash = 0;
+
+ /* Entry hash calculation. */
+ if (in_inode) {
+ __le32 crc32c_hash;
+
+ /*
+ * Feed crc32c hash instead of the raw value for entry
+ * hash calculation. This is to avoid walking
+ * potentially long value buffer again.
+ */
+ crc32c_hash = cpu_to_le32(
+ ext4_xattr_inode_get_hash(new_ea_inode));
+ hash = ext4_xattr_hash_entry(here->e_name,
+ here->e_name_len,
+ &crc32c_hash, 1);
+ } else if (is_block) {
+ __le32 *value = s->base + min_offs - new_size;
+
+ hash = ext4_xattr_hash_entry(here->e_name,
+ here->e_name_len, value,
+ new_size >> 2);
+ }
+ here->e_hash = hash;
}
+ if (is_block)
+ ext4_xattr_rehash((struct ext4_xattr_header *)s->base);
+
ret = 0;
out:
iput(old_ea_inode);
@@ -2421,9 +2459,7 @@ static int ext4_xattr_move_to_block(handle_t *handle,
struct inode *inode,
/* Save the entry name and the entry value */
if (entry->e_value_inum) {
- error = ext4_xattr_inode_get(inode,
- le32_to_cpu(entry->e_value_inum),
- buffer, value_size);
+ error = ext4_xattr_inode_get(inode, entry, buffer, value_size);
if (error)
goto out;
} else {
@@ -2913,30 +2949,22 @@ ext4_xattr_block_cache_find(struct inode *inode,
*
* Compute the hash of an extended attribute.
*/
-static void ext4_xattr_hash_entry(struct ext4_xattr_entry *entry,
- void *value_base)
+static __le32 ext4_xattr_hash_entry(char *name, size_t name_len, __le32 *value,
+ size_t value_count)
{
__u32 hash = 0;
- char *name = entry->e_name;
- int n;
- for (n = 0; n < entry->e_name_len; n++) {
+ while (name_len--) {
hash = (hash << NAME_HASH_SHIFT) ^
(hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
*name++;
}
-
- if (!entry->e_value_inum && entry->e_value_size) {
- __le32 *value = (__le32 *)((char *)value_base +
- le16_to_cpu(entry->e_value_offs));
- for (n = (le32_to_cpu(entry->e_value_size) +
- EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
- hash = (hash << VALUE_HASH_SHIFT) ^
- (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
- le32_to_cpu(*value++);
- }
+ while (value_count--) {
+ hash = (hash << VALUE_HASH_SHIFT) ^
+ (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
+ le32_to_cpu(*value++);
}
- entry->e_hash = cpu_to_le32(hash);
+ return cpu_to_le32(hash);
}
#undef NAME_HASH_SHIFT
--
2.13.1.508.gb3defc5cc-goog
------------------------------------------------------------------------------
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