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seccomp: don't leave dangling ->notif if file allocation fails

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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 <keescook@chromium.org>
Reported-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Tycho Andersen <tycho@tycho.pizza>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200902140953.1201956-1-tycho@tycho.pizza
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Tycho Andersen 2020-09-02 08:09:53 -06:00 committed by Kees Cook
parent 19d1d49f2a
commit e839317900
1 changed files with 8 additions and 3 deletions
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11
kernel/seccomp.c
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@ -1109,6 +1109,12 @@ out:
}
#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;
}