diff options
Diffstat (limited to 'ucount-Remove-the-atomicity-from-ucount-count.patch')
| -rw-r--r-- | ucount-Remove-the-atomicity-from-ucount-count.patch | 89 |
1 files changed, 0 insertions, 89 deletions
diff --git a/ucount-Remove-the-atomicity-from-ucount-count.patch b/ucount-Remove-the-atomicity-from-ucount-count.patch deleted file mode 100644 index 1b4e3c03f..000000000 --- a/ucount-Remove-the-atomicity-from-ucount-count.patch +++ /dev/null @@ -1,89 +0,0 @@ -From 040757f738e13caaa9c5078bca79aa97e11dde88 Mon Sep 17 00:00:00 2001 -From: "Eric W. Biederman" <ebiederm@xmission.com> -Date: Sun, 5 Mar 2017 15:03:22 -0600 -Subject: [PATCH] ucount: Remove the atomicity from ucount->count - -Always increment/decrement ucount->count under the ucounts_lock. The -increments are there already and moving the decrements there means the -locking logic of the code is simpler. This simplification in the -locking logic fixes a race between put_ucounts and get_ucounts that -could result in a use-after-free because the count could go zero then -be found by get_ucounts and then be freed by put_ucounts. - -A bug presumably this one was found by a combination of syzkaller and -KASAN. JongWhan Kim reported the syzkaller failure and Dmitry Vyukov -spotted the race in the code. - -Cc: stable@vger.kernel.org -Fixes: f6b2db1a3e8d ("userns: Make the count of user namespaces per user") -Reported-by: JongHwan Kim <zzoru007@gmail.com> -Reported-by: Dmitry Vyukov <dvyukov@google.com> -Reviewed-by: Andrei Vagin <avagin@gmail.com> -Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> ---- - include/linux/user_namespace.h | 2 +- - kernel/ucount.c | 18 +++++++++++------- - 2 files changed, 12 insertions(+), 8 deletions(-) - -diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h -index be76523..32354b4 100644 ---- a/include/linux/user_namespace.h -+++ b/include/linux/user_namespace.h -@@ -72,7 +72,7 @@ struct ucounts { - struct hlist_node node; - struct user_namespace *ns; - kuid_t uid; -- atomic_t count; -+ int count; - atomic_t ucount[UCOUNT_COUNTS]; - }; - -diff --git a/kernel/ucount.c b/kernel/ucount.c -index 62630a4..b4eeee0 100644 ---- a/kernel/ucount.c -+++ b/kernel/ucount.c -@@ -144,7 +144,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) - - new->ns = ns; - new->uid = uid; -- atomic_set(&new->count, 0); -+ new->count = 0; - - spin_lock_irq(&ucounts_lock); - ucounts = find_ucounts(ns, uid, hashent); -@@ -155,8 +155,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) - ucounts = new; - } - } -- if (!atomic_add_unless(&ucounts->count, 1, INT_MAX)) -+ if (ucounts->count == INT_MAX) - ucounts = NULL; -+ else -+ ucounts->count += 1; - spin_unlock_irq(&ucounts_lock); - return ucounts; - } -@@ -165,13 +167,15 @@ static void put_ucounts(struct ucounts *ucounts) - { - unsigned long flags; - -- if (atomic_dec_and_test(&ucounts->count)) { -- spin_lock_irqsave(&ucounts_lock, flags); -+ spin_lock_irqsave(&ucounts_lock, flags); -+ ucounts->count -= 1; -+ if (!ucounts->count) - hlist_del_init(&ucounts->node); -- spin_unlock_irqrestore(&ucounts_lock, flags); -+ else -+ ucounts = NULL; -+ spin_unlock_irqrestore(&ucounts_lock, flags); - -- kfree(ucounts); -- } -+ kfree(ucounts); - } - - static inline bool atomic_inc_below(atomic_t *v, int u) --- -2.9.3 - |