From 3a3f61ce5e0b4bcf730acc09c1af91012d241f85 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 29 Nov 2024 20:06:55 -0800 Subject: exec: Make sure task->comm is always NUL-terminated Using strscpy() meant that the final character in task->comm may be non-NUL for a moment before the "string too long" truncation happens. Instead of adding a new use of the ambiguous strncpy(), we'd want to use memtostr_pad() which enforces being able to check at compile time that sizes are sensible, but this requires being able to see string buffer lengths. Instead of trying to inline __set_task_comm() (which needs to call trace and perf functions), just open-code it. But to make sure we're always safe, add compile-time checking like we already do for get_task_comm(). Suggested-by: Linus Torvalds Suggested-by: "Eric W. Biederman" Signed-off-by: Kees Cook --- kernel/kthread.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/kthread.c b/kernel/kthread.c index db4ceb0f503c..162d55811744 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -736,10 +736,11 @@ EXPORT_SYMBOL(kthread_stop_put); int kthreadd(void *unused) { + static const char comm[TASK_COMM_LEN] = "kthreadd"; struct task_struct *tsk = current; /* Setup a clean context for our children to inherit. */ - set_task_comm(tsk, "kthreadd"); + set_task_comm(tsk, comm); ignore_signals(tsk); set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_TYPE_KTHREAD)); set_mems_allowed(node_states[N_MEMORY]); -- cgit v1.2.3