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Message-ID: <576DDC46.6050607@huawei.com>
Date: Sat, 25 Jun 2016 09:20:06 +0800
From: "Chenjie (K)" <chenjie6@...wei.com>
To: Michal Hocko <mhocko@...nel.org>
CC: <linux-mm@...ck.org>, <akpm@...ux-foundation.org>,
<linux-kernel@...r.kernel.org>, <David.Woodhouse@...el.com>,
<zhihui.gao@...wei.com>, <panxuesong@...wei.com>,
<akpm@...ux-foundation.org>
Subject: Re: [PATCH] memory:bugxfix panic on cat or write /dev/kmem
On 2016/6/23 20:42, Michal Hocko wrote:
> On Fri 24-06-16 01:30:10, chenjie6@...wei.com wrote:
>> From: chenjie <chenjie6@...wei.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
>
cat /dev/mem not panic. cat /dev/kmem, just the user's operation for
nothing.
>>
>> Signed-off-by: chenjie <chenjie6@...wei.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
>>
>> --
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>
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