From: Michal Hocko <mhocko@kernel.org>
To: chenjie6@huawei.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David.Woodhouse@intel.com, zhihui.gao@huawei.com,
panxuesong@huawei.com, akpm@linux-foundation.org
Subject: Re: [PATCH] memory:bugxfix panic on cat or write /dev/kmem
Date: Thu, 23 Jun 2016 14:42:58 +0200 [thread overview]
Message-ID: <20160623124257.GB30082@dhcp22.suse.cz> (raw)
In-Reply-To: <1466703010-32242-1-git-send-email-chenjie6@huawei.com>
On Fri 24-06-16 01:30:10, chenjie6@huawei.com wrote:
> From: chenjie <chenjie6@huawei.com>
>
> cat /dev/kmem and echo > /dev/kmem will lead panic
Writing to /dev/kmem without being extremely careful is a disaster AFAIK
and even reading from the file can lead to unexpected results. Anyway
I am trying to understand what exactly you are trying to fix here. Why
writing to/reading from zero pfn should be any special wrt. any other
potentially dangerous addresses
>
> Signed-off-by: chenjie <chenjie6@huawei.com>
> ---
> drivers/char/mem.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 71025c2..4bdde28 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -412,6 +412,8 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
> * by the kernel or data corruption may occur
> */
> kbuf = xlate_dev_kmem_ptr((void *)p);
> + if (!kbuf)
> + return -EFAULT;
>
> if (copy_to_user(buf, kbuf, sz))
> return -EFAULT;
> @@ -482,6 +484,11 @@ static ssize_t do_write_kmem(unsigned long p, const char __user *buf,
> * corruption may occur.
> */
> ptr = xlate_dev_kmem_ptr((void *)p);
> + if (!ptr) {
> + if (written)
> + break;
> + return -EFAULT;
> + }
>
> copied = copy_from_user(ptr, buf, sz);
> if (copied) {
> --
> 1.8.0
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-06-23 12:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-23 17:30 [PATCH] memory:bugxfix panic on cat or write /dev/kmem chenjie6
2016-06-23 12:42 ` Michal Hocko [this message]
2016-06-25 1:20 ` Chenjie (K)
2016-06-27 11:37 ` Michal Hocko
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