Merge branch 'for-6.14/constify-bin-attribute' into for-linus

- constification of 'struct bin_attribute' in various HID driver (Thomas Weißschuh)

1 files changed, 22 insertions, 6 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f0e9e00d3cf5..d380bffee2ef 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,9 +1121,12 @@ struct task_struct {
 	/*
 	 * executable name, excluding path.
 	 *
-	 * - normally initialized setup_new_exec()
-	 * - access it with [gs]et_task_comm()
-	 * - lock it with task_lock()
+	 * - normally initialized begin_new_exec()
+	 * - set it with set_task_comm()
+	 *   - strscpy_pad() to ensure it is always NUL-terminated and
+	 *     zero-padded
+	 *   - task_lock() to ensure the operation is atomic and the name is
+	 *     fully updated.
 	 */
 	char				comm[TASK_COMM_LEN];
 
@@ -1939,10 +1942,23 @@ static inline void set_task_comm(struct task_struct *tsk, const char *from)
 	__set_task_comm(tsk, from, false);
 }
 
-extern char *__get_task_comm(char *to, size_t len, struct task_struct *tsk);
+/*
+ * - Why not use task_lock()?
+ *   User space can randomly change their names anyway, so locking for readers
+ *   doesn't make sense. For writers, locking is probably necessary, as a race
+ *   condition could lead to long-term mixed results.
+ *   The strscpy_pad() in __set_task_comm() can ensure that the task comm is
+ *   always NUL-terminated and zero-padded. Therefore the race condition between
+ *   reader and writer is not an issue.
+ *
+ * - BUILD_BUG_ON() can help prevent the buf from being truncated.
+ *   Since the callers don't perform any return value checks, this safeguard is
+ *   necessary.
+ */
 #define get_task_comm(buf, tsk) ({			\
-	BUILD_BUG_ON(sizeof(buf) != TASK_COMM_LEN);	\
-	__get_task_comm(buf, sizeof(buf), tsk);		\
+	BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN);	\
+	strscpy_pad(buf, (tsk)->comm);			\
+	buf;						\
 })
 
 #ifdef CONFIG_SMP