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From: Christoph Hellwig <hch@lst.de>
To: Josef Bacik <josef@toxicpanda.com>
Cc: hch@lst.de, viro@ZenIV.linux.org.uk,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	kernel-team@fb.com, willy@infradead.org
Subject: Re: [PATCH][v2] proc: use vmalloc for our kernel buffer
Date: Thu, 13 Aug 2020 17:37:22 +0200	[thread overview]
Message-ID: <20200813153722.GA13844@lst.de> (raw)
In-Reply-To: <20200813153356.857625-1-josef@toxicpanda.com>

On Thu, Aug 13, 2020 at 11:33:56AM -0400, Josef Bacik wrote:
> Since
> 
>   sysctl: pass kernel pointers to ->proc_handler
> 
> we have been pre-allocating a buffer to copy the data from the proc
> handlers into, and then copying that to userspace.  The problem is this
> just blind kmalloc()'s the buffer size passed in from the read, which in
> the case of our 'cat' binary was 64kib.  Order-4 allocations are not
> awesome, and since we can potentially allocate up to our maximum order,
> use vmalloc for these buffers.
> 
> Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> v1->v2:
> - Make vmemdup_user_nul actually do the right thing...sorry about that.
> 
>  fs/proc/proc_sysctl.c  |  6 +++---
>  include/linux/string.h |  1 +
>  mm/util.c              | 27 +++++++++++++++++++++++++++
>  3 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index 6c1166ccdaea..207ac6e6e028 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -571,13 +571,13 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
>  		goto out;
>  
>  	if (write) {
> -		kbuf = memdup_user_nul(ubuf, count);
> +		kbuf = vmemdup_user_nul(ubuf, count);

Given that this can also do a kmalloc and thus needs to be paired
with kvfree shouldn't it be kvmemdup_user_nul?

  reply	other threads:[~2020-08-13 15:37 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-13 14:53 [PATCH] " Josef Bacik
2020-08-13 14:59 ` Matthew Wilcox
2020-08-13 15:08   ` Josef Bacik
2020-08-13 15:33 ` [PATCH][v2] " Josef Bacik
2020-08-13 15:37   ` Christoph Hellwig [this message]
2020-08-13 15:40     ` Josef Bacik
2020-08-13 15:41       ` Christoph Hellwig
2020-08-13 16:20         ` Al Viro
2020-08-13 17:19           ` Josef Bacik
2020-08-13 17:31             ` Al Viro
2020-08-13 17:36               ` Josef Bacik
2020-08-13 21:10             ` David Laight
2020-08-13 21:31               ` Josef Bacik
2020-08-13 16:19 ` [PATCH] " David Laight
2020-08-13 16:21   ` Al Viro
2020-08-13 17:08   ` Josef Bacik

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