linux-kernel - Re: [PATCH] printk: handle blank console arguments passed in.

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Date:   Tue, 17 Mar 2020 17:22:39 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Shreyas Joshi <shreyas.joshi@...mp.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "shreyasjoshi15@...il.com" <shreyasjoshi15@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] printk: handle blank console arguments passed in.

On (20/03/16 19:17), Shreyas Joshi wrote:
> 
> Thanks! I thought If we put a warning there then it won’t print anything.
> Please advise. I will send a new patch with the line wrapping to at most 75  once
> I know if I need to change anything more. 
> 

What I'm thinking about is turning "param=\0" into invalid case,
not just for printk(), for in general. Treat it as a NULL value.

Something like this, perhaps?

---
 init/main.c   | 4 ++++
 lib/cmdline.c | 8 ++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index d46b5673ecb4..46b732cd2615 100644
--- a/init/main.c
+++ b/init/main.c
@@ -673,6 +673,10 @@ static int __init do_early_param(char *param, char *val,
 		    (strcmp(param, "console") == 0 &&
 		     strcmp(p->str, "earlycon") == 0)
 		) {
+			if (!val && strchr(p->str, '=')) {
+				pr_warn("Malformed early option '%s'\n", param);
+				continue;
+			}
 			if (p->setup_func(val) != 0)
 				pr_warn("Malformed early option '%s'\n", param);
 		}
diff --git a/lib/cmdline.c b/lib/cmdline.c
index fbb9981a04a4..33fa0fc505a0 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -222,9 +222,9 @@ char *next_arg(char *args, char **param, char **val)
 	}
 
 	*param = args;
-	if (!equals)
+	if (!equals) {
 		*val = NULL;
-	else {
+	} else {
 		args[equals] = '\0';
 		*val = args + equals + 1;
 
@@ -244,6 +244,10 @@ char *next_arg(char *args, char **param, char **val)
 	} else
 		next = args + i;
 
+	/* Treat blank param value, e.g. 'param=', as NULL value. */
+	if (equals && **val == '\0')
+		*val = NULL;
+
 	/* Chew up trailing spaces. */
 	return skip_spaces(next);
 }
-- 
2.25.1.481.gfbce0eb801-goog