[PATCH 3/3] init/main.c: fix quoted value handling in unknown_bootoption

From: Arvind Sankar
Date: Sat Nov 23 2019 - 16:08:28 EST

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

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@xxxxxxxxxxxx>
init/main.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index a2008e7a797f..1ee92517c515 100644
--- a/init/main.c
+++ b/init/main.c
@@ -289,6 +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 */
@@ -296,7 +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)
@@ -310,7 +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))
envp_init[i] = param;