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

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Message-Id: <20240730051625.14349-1-viro@kernel.org>
Date: Tue, 30 Jul 2024 01:15:47 -0400
From: viro@...nel.org
To: linux-fsdevel@...r.kernel.org
Cc: amir73il@...il.com,
	bpf@...r.kernel.org,
	brauner@...nel.org,
	cgroups@...r.kernel.org,
	kvm@...r.kernel.org,
	netdev@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: [PATCH 01/39] memcg_write_event_control(): fix a user-triggerable oops

From: Al Viro <viro@...iv.linux.org.uk>

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 <viro@...iv.linux.org.uk>
---
 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