[PATCH] kobject_uevent: remove warning in init_uevent_argv()

[Greg Kroah-Hartman]

syzbot can trigger the WARN() in init_uevent_argv() which isn't the
nicest as the code does properly recover and handle the error.  So
change the WARN() call to pr_warn() and provide some more information on
what the buffer size that was needed.

Link: https://lore.kernel.org/r/20201107082206.GA19079@xxxxxxxxx
Reported-by: syzbot+92340f7b2b4789907fdb@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 lib/kobject_uevent.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7998affa45d4..c87d5b6a8a55 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -251,12 +251,13 @@ static int kobj_usermode_filter(struct kobject *kobj)
 
 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
 {
+	int buffer_size = sizeof(env->buf) - env->buflen;
 	int len;
 
-	len = strlcpy(&env->buf[env->buflen], subsystem,
-		      sizeof(env->buf) - env->buflen);
-	if (len >= (sizeof(env->buf) - env->buflen)) {
-		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
+	len = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
+	if (len >= buffer_size) {
+		pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
+			buffer_size, len);
 		return -ENOMEM;
 	}
 
-- 
2.31.1