From: Benjamin LaHaise <bcrl@kvack.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Jan Kara <jack@suse.cz>, Alexander Viro <viro@zeniv.linux.org.uk>,
linux-aio <linux-aio@kvack.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>,
Sasha Levin <sasha.levin@oracle.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>
Subject: Re: int overflow in io_getevents
Date: Wed, 6 Jan 2016 13:01:58 -0500 [thread overview]
Message-ID: <20160106180158.GE4439@kvack.org> (raw)
In-Reply-To: <CACT4Y+auqXikZzMW327NNSkESYsvhJouVVW7o5ycPP_g-MgnKQ@mail.gmail.com>
On Wed, Dec 16, 2015 at 07:38:33PM +0100, Dmitry Vyukov wrote:
> > Yup, looks correct. Will you send a patch?
>
> I've drafted the verification:
>
> @@ -1269,6 +1269,8 @@ static long read_events(struct kioctx *ctx, long
> min_nr, long nr,
>
> if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
> return -EFAULT;
> + if (!timespec_valid_strict(&strict))
> + return -EINVAL;
>
> until = timespec_to_ktime(ts);
> }
>
> But now I am thinking whether it is the right solution.
> First, user does not know about KTIME_MAX, so it is not unreasonable
> to pass timespec{INT64_MAX, INT64_MAX} as timeout expecting that it
> will block for a long time. And it actually probably mostly works now,
> because after the overflow you still get something large with high
> probability. If we do the fix, then users will need to pass seconds <
> KTIME_MAX, while they don't know KTIME_MAX value.
> Second, there seems to be more serious issue in ktime_set() which
> checks seconds for KTIME_MAX, but on the next line addition still
> overflows int64.
> Thoughts?
I finally had some time to look over this after the holidays, and I
don't think using timespec_valid_strict() is the right approach here,
as userspace will have no idea what KTIME_MAX is. Instead, I think the
right approach is to -EINVAL for negative values (which should avoid
the overflow), and to allow too large values to be silently truncated
by timespec_to_ktime(). The truncation doesn't matter all that much
given that it's in the hundreds of years ballpark. I'll push the patch
below if there are no objections.
-ben
--
"Thought is the essence of where you are now."
commit 4304367826d0df42086ef24428c6c277acd822a9
Author: Benjamin LaHaise <bcrl@kvack.org>
Date: Wed Jan 6 12:46:12 2016 -0500
aio: handle integer overflow in io_getevents() timespec usage
Dmitry Vyukov reported an integer overflow in io_getevents() when
running a fuzzer. Upon investigation, the triggers appears to be that a
negative value for the tv_sec or tv_nsec was passed in which is not
handled by timespec_to_ktime(). This patch fixes that by making
io_getevents() return -EINVAL when negative timeouts are passed in.
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
diff --git a/fs/aio.c b/fs/aio.c
index 155f842..f325ed4 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1269,6 +1269,8 @@ static long read_events(struct kioctx *ctx, long min_nr, long nr,
if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
return -EFAULT;
+ if ((ts.tv_sec < 0) || (ts.tv_nsec < 0))
+ return -EINVAL;
until = timespec_to_ktime(ts);
}
next prev parent reply other threads:[~2016-01-06 18:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-07 10:27 int overflow in io_getevents Dmitry Vyukov
2015-12-16 12:56 ` Jan Kara
2015-12-16 18:38 ` Dmitry Vyukov
2015-12-18 8:15 ` Jan Kara
2016-01-06 18:01 ` Benjamin LaHaise [this message]
2016-01-07 9:12 ` Dmitry Vyukov
2016-01-07 15:31 ` Benjamin LaHaise
2016-01-07 15:37 ` Dmitry Vyukov
2016-01-07 15:52 ` Benjamin LaHaise
2016-01-07 16:27 ` Dmitry Vyukov
2016-10-26 11:44 ` Jiri Slaby
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