seccomp: Add find_notification helper
This adds a helper which can iterate through a seccomp_filter to
find a notification matching an ID. It removes several replicated
chunks of code.
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Tycho Andersen <tycho@tycho.ws>
Cc: Matt Denton <mpdenton@google.com>
Cc: Kees Cook <keescook@google.com>,
Cc: Jann Horn <jannh@google.com>,
Cc: Robert Sesek <rsesek@google.com>,
Cc: Chris Palmer <palmer@google.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Tycho Andersen <tycho@tycho.ws>
Link: https://lore.kernel.org/r/20200601112532.150158-1-sargun@sargun.me
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index f387e50..e711d69 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -41,6 +41,7 @@
#include <linux/tracehook.h>
#include <linux/uaccess.h>
#include <linux/anon_inodes.h>
+#include <linux/lockdep.h>
enum notify_state {
SECCOMP_NOTIFY_INIT,
@@ -1024,6 +1025,23 @@ static int seccomp_notify_release(struct inode *inode, struct file *file)
return 0;
}
+/* must be called with notif_lock held */
+static inline struct seccomp_knotif *
+find_notification(struct seccomp_filter *filter, u64 id)
+{
+ struct seccomp_knotif *cur;
+
+ lockdep_assert_held(&filter->notify_lock);
+
+ list_for_each_entry(cur, &filter->notif->notifications, list) {
+ if (cur->id == id)
+ return cur;
+ }
+
+ return NULL;
+}
+
+
static long seccomp_notify_recv(struct seccomp_filter *filter,
void __user *buf)
{
@@ -1081,15 +1099,8 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
* may have died when we released the lock, so we need to make
* sure it's still around.
*/
- knotif = NULL;
mutex_lock(&filter->notify_lock);
- list_for_each_entry(cur, &filter->notif->notifications, list) {
- if (cur->id == unotif.id) {
- knotif = cur;
- break;
- }
- }
-
+ knotif = find_notification(filter, unotif.id);
if (knotif) {
knotif->state = SECCOMP_NOTIFY_INIT;
up(&filter->notif->request);
@@ -1104,7 +1115,7 @@ static long seccomp_notify_send(struct seccomp_filter *filter,
void __user *buf)
{
struct seccomp_notif_resp resp = {};
- struct seccomp_knotif *knotif = NULL, *cur;
+ struct seccomp_knotif *knotif;
long ret;
if (copy_from_user(&resp, buf, sizeof(resp)))
@@ -1121,13 +1132,7 @@ static long seccomp_notify_send(struct seccomp_filter *filter,
if (ret < 0)
return ret;
- list_for_each_entry(cur, &filter->notif->notifications, list) {
- if (cur->id == resp.id) {
- knotif = cur;
- break;
- }
- }
-
+ knotif = find_notification(filter, resp.id);
if (!knotif) {
ret = -ENOENT;
goto out;
@@ -1153,7 +1158,7 @@ static long seccomp_notify_send(struct seccomp_filter *filter,
static long seccomp_notify_id_valid(struct seccomp_filter *filter,
void __user *buf)
{
- struct seccomp_knotif *knotif = NULL;
+ struct seccomp_knotif *knotif;
u64 id;
long ret;
@@ -1164,16 +1169,12 @@ static long seccomp_notify_id_valid(struct seccomp_filter *filter,
if (ret < 0)
return ret;
- ret = -ENOENT;
- list_for_each_entry(knotif, &filter->notif->notifications, list) {
- if (knotif->id == id) {
- if (knotif->state == SECCOMP_NOTIFY_SENT)
- ret = 0;
- goto out;
- }
- }
+ knotif = find_notification(filter, id);
+ if (knotif && knotif->state == SECCOMP_NOTIFY_SENT)
+ ret = 0;
+ else
+ ret = -ENOENT;
-out:
mutex_unlock(&filter->notify_lock);
return ret;
}