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Message-ID: <685d850347a1191bba8ba7766fc409b140d18f03.camel@perches.com>
Subject: Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
From:   Joe Perches <joe@perches.com>
To:     "Michael S. Tsirkin" <mst@redhat.com>,
        Bartosz Golaszewski <brgl@bgdev.pl>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Gustavo Padovan <gustavo@padovan.org>,
        Christian =?ISO-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Tony Luck <tony.luck@intel.com>,
        James Morse <james.morse@arm.com>,
        Robert Richter <rric@kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Jason Wang <jasowang@redhat.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, linux-media@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org,
        linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
        linux-gpio@vger.kernel.org, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-mm@kvack.org, alsa-devel@alsa-project.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Tue, 27 Oct 2020 09:50:36 -0700
In-Reply-To: <20201027112607-mutt-send-email-mst@kernel.org>
References: <20201027121725.24660-1-brgl@bgdev.pl>
         <20201027121725.24660-4-brgl@bgdev.pl>
         <20201027112607-mutt-send-email-mst@kernel.org>
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On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
> On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > 
> > Use the helper that checks for overflows internally instead of manually
> > calculating the size of the new array.
> > 
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> No problem with the patch, it does introduce some symmetry in the code.

Perhaps more symmetry by using kmemdup
---
 drivers/vhost/vringh.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 8bd8b403f087..99222a3651cd 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh,
 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
 {
 	struct kvec *new;
-	unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
+	size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
+	size_t size;
 
 	if (new_num < 8)
 		new_num = 8;
 
-	flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
-	if (flag)
-		new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
-	else {
-		new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
-		if (new) {
-			memcpy(new, iov->iov,
-			       iov->max_num * sizeof(struct iovec));
-			flag = VRINGH_IOV_ALLOCATED;
-		}
-	}
+	if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec), &size)))
+		return -ENOMEM;
+
+	if (iov->max_num & VRINGH_IOV_ALLOCATED)
+		new = krealloc(iov->iov, size, gfp);
+	else
+		new = kmemdup(iov->iov, size, gfp);
 	if (!new)
 		return -ENOMEM;
 	iov->iov = new;
-	iov->max_num = (new_num | flag);
+	iov->max_num = new_num | VRINGH_IOV_ALLOCATED;
 	return 0;
 }