Subject: [PATCH 01/39] memcg_write_event_control(): fix a user-triggerable oops

From: [email-masked]
Date: Tue, 30 Jul 2024 01:15:47 -0400

From: Al Viro <[email-masked]>

we are *not* guaranteed that anything past the terminating NUL
is mapped (let alone initialized with anything sane).

[the sucker got moved in mainline]

Signed-off-by: Al Viro <[email-masked]>
---
 mm/memcontrol-v1.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 2aeea4d8bf8e..417c96f2da28 100644
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -1842,9 +1842,12 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
 	buf = endp + 1;
 
 	cfd = simple_strtoul(buf, &endp, 10);
-	if ((*endp != ' ') && (*endp != '\0'))
+	if (*endp == '\0')
+		buf = endp;
+	else if (*endp == ' ')
+		buf = endp + 1;
+	else
 		return -EINVAL;
-	buf = endp + 1;
 
 	event = kzalloc(sizeof(*event), GFP_KERNEL);
 	if (!event)
-- 
2.39.2