f2fs: check entire encrypted bigname when finding a dentry

commit 6332cd32c8290a80e929fc044dc5bdba77396e33 upstream.

If user has no key under an encrypted dir, fscrypt gives digested dentries.
Previously, when looking up a dentry, f2fs only checks its hash value with
first 4 bytes of the digested dentry, which didn't handle hash collisions fully.
This patch enhances to check entire dentry bytes likewise ext4.

Eric reported how to reproduce this issue by:

 # seq -f "edir/abcdefghijklmnopqrstuvwxyz012345%.0f" 100000 | xargs touch
 # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
100000
 # sync
 # echo 3 > /proc/sys/vm/drop_caches
 # keyctl new_session
 # find edir -type f | xargs stat -c %i | sort | uniq | wc -l
99999

Cc: <stable@vger.kernel.org>
Reported-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(fixed f2fs_dentry_hash() to work even when the hash is 0)
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 31 insertions, 20 deletions

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index ebdc90fc71b7..e32d82b011a9 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -130,19 +130,29 @@ struct f2fs_dir_entry *find_target_dentry(struct fscrypt_name *fname,
                         continue;
                 }
 
-                /* encrypted case */
+                if (de->hash_code != namehash)
+                        goto not_match;
+
                 de_name.name = d->filename[bit_pos];
                 de_name.len = le16_to_cpu(de->name_len);
 
-                /* show encrypted name */
-                if (fname->hash) {
-                        if (de->hash_code == fname->hash)
-                                goto found;
-                } else if (de_name.len == name->len &&
-                        de->hash_code == namehash &&
-                        !memcmp(de_name.name, name->name, name->len))
+#ifdef CONFIG_F2FS_FS_ENCRYPTION
+                if (unlikely(!name->name)) {
+                        if (fname->usr_fname->name[0] == '_') {
+                                if (de_name.len >= 16 &&
+                                        !memcmp(de_name.name + de_name.len - 16,
+                                                fname->crypto_buf.name + 8, 16))
+                                        goto found;
+                                goto not_match;
+                        }
+                        name->name = fname->crypto_buf.name;
+                        name->len = fname->crypto_buf.len;
+                }
+#endif
+                if (de_name.len == name->len &&
+                                !memcmp(de_name.name, name->name, name->len))
                         goto found;
-
+not_match:
                 if (max_slots && max_len > *max_slots)
                         *max_slots = max_len;
                 max_len = 0;
@@ -170,12 +180,7 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir,
         struct f2fs_dir_entry *de = NULL;
         bool room = false;
         int max_slots;
-        f2fs_hash_t namehash;
-
-        if(fname->hash)
-                namehash = cpu_to_le32(fname->hash);
-        else
-                namehash = f2fs_dentry_hash(&name);
+        f2fs_hash_t namehash = f2fs_dentry_hash(&name, fname);
 
         nbucket = dir_buckets(level, F2FS_I(dir)->i_dir_level);
         nblock = bucket_blocks(level);
@@ -539,7 +544,7 @@ int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
 
         level = 0;
         slots = GET_DENTRY_SLOTS(new_name->len);
-        dentry_hash = f2fs_dentry_hash(new_name);
+        dentry_hash = f2fs_dentry_hash(new_name, NULL);
 
         current_depth = F2FS_I(dir)->i_current_depth;
         if (F2FS_I(dir)->chash == dentry_hash) {
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 3a1640be7ffc..c12f695923b6 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2016,7 +2016,8 @@ int sanity_check_ckpt(struct f2fs_sb_info *sbi);
 /*
  * hash.c
  */
-f2fs_hash_t f2fs_dentry_hash(const struct qstr *);
+f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
+                                struct fscrypt_name *fname);
 
 /*
  * node.c
diff --git a/fs/f2fs/hash.c b/fs/f2fs/hash.c
index 71b7206c431e..eb2e031ea887 100644
--- a/fs/f2fs/hash.c
+++ b/fs/f2fs/hash.c
@@ -70,7 +70,8 @@ static void str2hashbuf(const unsigned char *msg, size_t len,
                 *buf++ = pad;
 }
 
-f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info)
+f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
+                                struct fscrypt_name *fname)
 {
         __u32 hash;
         f2fs_hash_t f2fs_hash;
@@ -79,6 +80,10 @@ f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info)
         const unsigned char *name = name_info->name;
         size_t len = name_info->len;
 
+        /* encrypted bigname case */
+        if (fname && !fname->disk_name.name)
+                return cpu_to_le32(fname->hash);
+
         if (is_dot_dotdot(name_info))
                 return 0;
 
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 5f1a67f756af..a21faa1c6817 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -294,7 +294,7 @@ struct f2fs_dir_entry *find_in_inline_dir(struct inode *dir,
                 return NULL;
         }
 
-        namehash = f2fs_dentry_hash(&name);
+        namehash = f2fs_dentry_hash(&name, fname);
 
         inline_dentry = inline_data_addr(ipage);
 
@@ -531,7 +531,7 @@ int f2fs_add_inline_entry(struct inode *dir, const struct qstr *new_name,
 
         f2fs_wait_on_page_writeback(ipage, NODE, true);
 
-        name_hash = f2fs_dentry_hash(new_name);
+        name_hash = f2fs_dentry_hash(new_name, NULL);
         make_dentry_ptr(NULL, &d, (void *)dentry_blk, 2);
         f2fs_update_dentry(ino, mode, &d, new_name, name_hash, bit_pos);