Christian and Kees both pointed out that this is a bit sloppy to open-code both places, and Christian points out that we leave a dangling pointer to ->notif if file allocation fails. Since we check ->notif for null in order to determine if it's ok to install a filter, this means people won't be able to install a filter if the file allocation fails for some reason, even if they subsequently should be able to.
To fix this, let's hoist this free+null into its own little helper and use it. Reported-by: Kees Cook <keesc...@chromium.org> Reported-by: Christian Brauner <christian.brau...@ubuntu.com> Signed-off-by: Tycho Andersen <tycho@tycho.pizza> --- kernel/seccomp.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index bb0dd9ae699a..676d4af62103 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -1109,6 +1109,12 @@ static long seccomp_set_mode_strict(void) } #ifdef CONFIG_SECCOMP_FILTER +static void seccomp_notify_free(struct seccomp_filter *filter) +{ + kfree(filter->notif); + filter->notif = NULL; +} + static void seccomp_notify_detach(struct seccomp_filter *filter) { struct seccomp_knotif *knotif; @@ -1138,8 +1144,7 @@ static void seccomp_notify_detach(struct seccomp_filter *filter) complete(&knotif->ready); } - kfree(filter->notif); - filter->notif = NULL; + seccomp_notify_free(filter); mutex_unlock(&filter->notify_lock); } @@ -1494,7 +1499,7 @@ static struct file *init_listener(struct seccomp_filter *filter) out_notif: if (IS_ERR(ret)) - kfree(filter->notif); + seccomp_notify_free(filter); out: return ret; } base-commit: 7b6aa0bb62fd6fd50f2d14136136262d28fb2dfe -- 2.25.1