[PATCH] usermodehelper: Fix -ENOMEM return logic

Lucas De Marchi
2013-02-25T14:33:27Z

Callers of call_usermodehelper_fns() should check the return value and
free themselves the data passed if the return is -ENOMEM. This is
because the subprocess_info is allocated in this function, and if the
allocation fail, the cleanup function cannot be called.

However call_usermodehelper_exec() may also return -ENOMEM, in which
case the cleanup function is called. This means that if the caller
checked the return code, it was risking running the cleanup twice (like
kernel/sys.c:orderly_poweroff()) and if not, a leak could happen.

This patch fixes both call_usermodehelper_fns() to never call the
cleanup function in case retval == -ENOMEM and also the callers to
actually check the return value of this function.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
---
kernel/kmod.c | 9 +++++++--
security/keys/request_key.c | 10 +++++++---
2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 56dd349..c4fec52 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -77,6 +77,7 @@ static void free_modprobe_argv(struct subprocess_info *info)

static int call_modprobe(char *module_name, int wait)
{
+ int ret;
static char *envp[] = {
"HOME=/",
"TERM=linux",
@@ -98,8 +99,12 @@ static int call_modprobe(char *module_name, int wait)
argv[3] = module_name; /* check free_modprobe_argv() */
argv[4] = NULL;

- return call_usermodehelper_fns(modprobe_path, argv, envp,
+ ret = call_usermodehelper_fns(modprobe_path, argv, envp,
wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
+ if (ret != -ENOMEM)
+ return ret;
+
+ kfree(module_name);
free_argv:
kfree(argv);
out:
@@ -249,7 +254,7 @@ static int call_helper(void *data)

static void call_usermodehelper_freeinfo(struct subprocess_info *info)
{
- if (info->cleanup)
+ if (info->cleanup && info->retval != -ENOMEM)
(*info->cleanup)(info);
kfree(info);
}
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 4bd6bdb..22dc7a4 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -93,9 +93,13 @@ static void umh_keys_cleanup(struct subprocess_info *info)
static int call_usermodehelper_keys(char *path, char **argv, char **envp,
struct key *session_keyring, int wait)
{
- return call_usermodehelper_fns(path, argv, envp, wait,
- umh_keys_init, umh_keys_cleanup,
- key_get(session_keyring));
+ int ret = call_usermodehelper_fns(path, argv, envp, wait,
+ umh_keys_init, umh_keys_cleanup,
+ key_get(session_keyring));
+ if (ret == -ENOMEM)
+ key_put(session_keyring);
+
+ return ret;
}

/*
--
1.8.1.4