exfat: check if filename entries exceeds max filename length

commit d42334578eba1390859012ebb91e1e556d51db49 upstream.

exfat_extract_uni_name copies characters from a given file name entry into
the 'uniname' variable. This variable is actually defined on the stack of
the exfat_readdir() function. According to the definition of
the 'exfat_uni_name' type, the file name should be limited 255 characters
(+ null teminator space), but the exfat_get_uniname_from_ext_entry()
function can write more characters because there is no check if filename
entries exceeds max filename length. This patch add the check not to copy
filename characters when exceeding max filename length.

Cc: stable@vger.kernel.org
Cc: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reported-by: Maxim Suhanov <dfirblog@gmail.com>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[Harshit: backport to 5.15.y]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 8475a8653c3a4c0a0fe596bfed41d4551dcf7c11..f6dd4fc8eaf455f24e72c1c4975abf880c4b3286 100644 (file)
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -34,6 +34,7 @@ static void exfat_get_uniname_from_ext_entry(struct super_block *sb,
 {
        int i;
        struct exfat_entry_set_cache *es;
+       unsigned int uni_len = 0, len;
 
        es = exfat_get_dentry_set(sb, p_dir, entry, ES_ALL_ENTRIES);
        if (!es)
@@ -52,7 +53,10 @@ static void exfat_get_uniname_from_ext_entry(struct super_block *sb,
                if (exfat_get_entry_type(ep) != TYPE_EXTEND)
                        break;
 
-               exfat_extract_uni_name(ep, uniname);
+               len = exfat_extract_uni_name(ep, uniname);
+               uni_len += len;
+               if (len != EXFAT_FILE_NAME_LEN || uni_len >= MAX_NAME_LENGTH)
+                       break;
                uniname += EXFAT_FILE_NAME_LEN;
        }
 
@@ -1032,7 +1036,8 @@ rewind:
                        if (entry_type == TYPE_EXTEND) {
                                unsigned short entry_uniname[16], unichar;
 
-                               if (step != DIRENT_STEP_NAME) {
+                               if (step != DIRENT_STEP_NAME ||
+                                   name_len >= MAX_NAME_LENGTH) {
                                        step = DIRENT_STEP_FILE;
                                        continue;
                                }