+ proc-use-strnlen-for-name-validation-in-__proc_create.patch added to mm-nonmm-unstable branch

+ proc-use-strnlen-for-name-validation-in-__proc_create.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: proc: use strnlen() for name validation in __proc_create
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     proc-use-strnlen-for-name-validation-in-__proc_create.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/proc-use-strnlen-for-name-validation-in-__proc_create.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Thorsten Blum <thorsten.blum@linux.dev>
Subject: proc: use strnlen() for name validation in __proc_create
Date: Tue, 21 Apr 2026 14:26:47 +0200

Replace strlen(fn) with strnlen(fn, NAME_MAX + 1) when validating the
final path component in __proc_create().

This preserves the existing name limit while bounding the length scan to
one byte past the maximum name length.  Handle empty names separately, and
treat names longer than NAME_MAX as too long.

Link: https://lore.kernel.org/20260421122648.56723-2-thorsten.blum@linux.dev
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Thorsten Blum <thorsten.blum@linux.dev>
Cc: wangzijie <wangzijie1@honor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/generic.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/proc/generic.c~proc-use-strnlen-for-name-validation-in-__proc_create
+++ a/fs/proc/generic.c
@@ -427,9 +427,13 @@ static struct proc_dir_entry *__proc_cre
 	if (xlate_proc_name(name, parent, &fn) != 0)
 		goto out;
 	qstr.name = fn;
-	qstr.len = strlen(fn);
-	if (qstr.len == 0 || qstr.len >= 256) {
-		WARN(1, "name len %u\n", qstr.len);
+	qstr.len = strnlen(fn, NAME_MAX + 1);
+	if (qstr.len == 0) {
+		WARN(1, "empty name\n");
+		return NULL;
+	}
+	if (qstr.len > NAME_MAX) {
+		WARN(1, "name too long\n");
 		return NULL;
 	}
 	if (qstr.len == 1 && fn[0] == '.') {
_

Patches currently in -mm which might be from thorsten.blum@linux.dev are

proc-use-strnlen-for-name-validation-in-__proc_create.patch