From: Dan Carpenter <dan.carpenter@oracle.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>,
Stefan Wahren <stefan.wahren@i2se.com>,
Ojaswin Mujoo <ojaswin98@gmail.com>,
Phil Elwell <phil@raspberrypi.com>,
Amarjargal Gundjalam <amarjargal16@gmail.com>,
bcm-kernel-feedback-list@broadcom.com,
linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] staging: vc04_services: shut up out-of-range warning
Date: Mon, 27 Sep 2021 15:26:58 +0300 [thread overview]
Message-ID: <20210927122658.GF2048@kadam> (raw)
In-Reply-To: <20210927113702.3866843-1-arnd@kernel.org>
On Mon, Sep 27, 2021 at 01:36:56PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The comparison against SIZE_MAX produces a harmless warning on 64-bit
> architectures:
>
> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:185:16: error: result of comparison of constant 419244183493398898 with expression of type 'unsigned int' is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Shut up that warning by adding a cast to a longer type.
>
> Fixes: ca641bae6da9 ("staging: vc04_services: prevent integer overflow in create_pagelist()")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index b25369a13452..967f10b9582a 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -182,7 +182,7 @@ create_pagelist(char *buf, char __user *ubuf,
> offset = (uintptr_t)ubuf & (PAGE_SIZE - 1);
> num_pages = DIV_ROUND_UP(count + offset, PAGE_SIZE);
>
> - if (num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> + if ((size_t)num_pages > (SIZE_MAX - sizeof(struct pagelist) -
> sizeof(struct vchiq_pagelist_info)) /
> (sizeof(u32) + sizeof(pages[0]) +
> sizeof(struct scatterlist)))
The temptation would be to declare "num_pages" as size_t instead of
adding this cost. But then something will complain about the
"pagelistinfo->num_pages = num_pages;" assignment because
"pagelistinfo->num_pages" is a u32.
The next temptation is to change the SIZE_MAX to UINT_MAX. I didn't
do that originally because I can't test this and I was trying not to
break things... We probably still don't want to break things, but maybe
there is someone who is more familiar with this who knows if UINT_MAX is
okay?
regards,
dan carpenter
next prev parent reply other threads:[~2021-09-27 12:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 11:36 [PATCH] staging: vc04_services: shut up out-of-range warning Arnd Bergmann
2021-09-27 12:26 ` Dan Carpenter [this message]
2021-09-27 13:21 ` Phil Elwell
2021-09-27 20:37 ` Arnd Bergmann
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