exfat: check if filename entries exceeds max filename length

[ Upstream commit d42334578eba1390859012ebb91e1e556d51db49 ]

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>

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 78de6f67f882d81529510fc82b55a702d2d5c01e..51b03b0dd5f75220f3a66a866614cb061fc121d6 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;
        }
 
@@ -1024,7 +1028,8 @@ 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;
                                }