From e839317900e9f13c83d8711d684de88c625b307a Mon Sep 17 00:00:00 2001
From: Tycho Andersen <tycho@tycho.pizza>
Date: Wed, 2 Sep 2020 08:09:53 -0600
Subject: [PATCH] seccomp: don't leave dangling ->notif if file allocation
fails
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>
---
kernel/seccomp.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index bb0dd9ae699a4d..676d4af621038a 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -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;
}
--
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