memcg_write_event_control(): fix a user-triggerable oops

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

Fixes: 0dea116876 ("cgroup: implement eventfd-based generic API for notifications")
Cc: stable@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2024-07-21 14:45:08 -04:00
parent 9a2fa14720
commit 046667c4d3

View File

@ -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)