FAILED: patch "[PATCH] exfat: check if filename entries exceeds max filename length" failed to apply to 5.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x d42334578eba1390859012ebb91e1e556d51db49
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023080735-headsman-grandpa-be68@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

d42334578eba ("exfat: check if filename entries exceeds max filename length")
20914ff6dd56 ("exfat: move exfat_entry_set_cache from heap to stack")
a3ff29a95fde ("exfat: support dynamic allocate bh for exfat_entry_set_cache")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From d42334578eba1390859012ebb91e1e556d51db49 Mon Sep 17 00:00:00 2001
From: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Date: Thu, 13 Jul 2023 21:59:37 +0900
Subject: [PATCH] exfat: check if filename entries exceeds max filename length

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@xxxxxxxxxxxxxxx
Cc: Yuezhang Mo <Yuezhang.Mo@xxxxxxxx>
Reported-by: Maxim Suhanov <dfirblog@xxxxxxxxx>
Reviewed-by: Sungjong Seo <sj1557.seo@xxxxxxxxxxx>
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 957574180a5e..bc48f3329921 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -34,6 +34,7 @@ static int exfat_get_uniname_from_ext_entry(struct super_block *sb,
 {
 	int i, err;
 	struct exfat_entry_set_cache es;
+	unsigned int uni_len = 0, len;
 
 	err = exfat_get_dentry_set(&es, sb, p_dir, entry, ES_ALL_ENTRIES);
 	if (err)
@@ -52,7 +53,10 @@ static int 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;
 	}
 
@@ -1079,7 +1083,8 @@ int exfat_find_dir_entry(struct super_block *sb, struct exfat_inode_info *ei,
 			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;
 				}