linux-kernel - [PATCH v2 3/3] init/main.c: fix quoted value handling in unknown

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Date:   Thu, 12 Dec 2019 13:00:23 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] init/main.c: fix quoted value handling in unknown_bootoption

Commit a99cd1125189 ("init: fix bug where environment vars can't be
passed via boot args") introduced two minor bugs in unknown_bootoption
by factoring out the quoted value handling into a separate function.

When value is quoted, repair_env_string will move the value up 1 byte to
strip the quotes, so val in unknown_bootoption no longer points to the
actual location of the value.

The result is that an argument of the form param=".value" is mistakenly
treated as a potential module parameter and is not placed in init's
environment, and an argument of the form param="value" can result in a
duplicate environment variable: eg TERM="vt100" on the command line will
result in both TERM=linux and TERM=vt100 being placed into init's
environment.

Fix this by recording the length of the param before calling
repair_env_string instead of relying on val.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 init/main.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/init/main.c b/init/main.c
index a1febc3de582..efece9fe988e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -255,7 +255,6 @@ static void __init repair_env_string(char *param, char *val)
 		else if (val == param+strlen(param)+2) {
 			val[-2] = '=';
 			memmove(val-1, val, strlen(val)+1);
-			val--;
 		} else
 			BUG();
 	}
@@ -290,6 +289,8 @@ static int __init set_init_arg(char *param, char *val,
 static int __init unknown_bootoption(char *param, char *val,
 				     const char *unused, void *arg)
 {
+	size_t len = strlen(param);
+
 	repair_env_string(param, val);

 	/* Handle obsolete-style parameters */
@@ -297,7 +298,7 @@ static int __init unknown_bootoption(char *param, char *val,
 		return 0;

 	/* Unused module parameter. */
-	if (strchr(param, '.') && (!val || strchr(param, '.') < val))
+	if (strnchr(param, len, '.'))
 		return 0;

 	if (panic_later)
@@ -311,7 +312,7 @@ static int __init unknown_bootoption(char *param, char *val,
 				panic_later = "env";
 				panic_param = param;
 			}
-			if (!strncmp(param, envp_init[i], val - param))
+			if (!strncmp(param, envp_init[i], len+1))
 				break;
 		}
 		envp_init[i] = param;
-- 
2.23.0