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[trusty/master-next,1/1] futex: Prevent overflow by strengthen input validation

Message ID 20180601090612.31073-3-apw@canonical.com
State New
Headers show

Commit Message

Andy Whitcroft June 1, 2018, 9:06 a.m. UTC 
From: Li Jinyue <lijinyue@huawei.com>

UBSAN reports signed integer overflow in kernel/futex.c:

 UBSAN: Undefined behaviour in kernel/futex.c:2041:18
 signed integer overflow:
 0 - -2147483648 cannot be represented in type 'int'

Add a sanity check to catch negative values of nr_wake and nr_requeue.

Signed-off-by: Li Jinyue <lijinyue@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: dvhart@infradead.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1513242294-31786-1-git-send-email-lijinyue@huawei.com

(backported from commit fbe0e839d1e22d88810f3ee3e2f1479be4c0aa4a)
CVE-2018-6927
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
 kernel/futex.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/kernel/futex.c b/kernel/futex.c
index af6bdd842e06..26fe00d4b57f 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1385,6 +1385,9 @@  static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
 	struct plist_head *head1;
 	struct futex_q *this, *next;
 
+	if (nr_wake < 0 || nr_requeue < 0)
+		return -EINVAL;
+
 	if (requeue_pi) {
 		/*
 		 * Requeue PI only works on two distinct uaddrs. This