linux-kernel - Re: [PATCH] staging: lustre: replace kzalloc with copy_from_user with memdup

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Date:	Tue, 31 Mar 2015 17:57:56 +0200
From:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	"Dhere, Chaitanya (C.)" <cvijaydh@...teon.com>,
	"oleg.drokin@...el.com" <oleg.drokin@...el.com>,
	"andreas.dilger@...el.com" <andreas.dilger@...el.com>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"jinshan.xiong@...el.com" <jinshan.xiong@...el.com>,
	"aybuke.147@...il.com" <aybuke.147@...il.com>,
	"john.hammond@...el.com" <john.hammond@...el.com>,
	"HPDD-discuss@...ts.01.org" <HPDD-discuss@...1.01.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: lustre: replace kzalloc with copy_from_user
 with memdup_user

On Tue, Mar 31, 2015 at 05:15:23PM +0200, Julia Lawall wrote:
> On Tue, 31 Mar 2015, Dhere, Chaitanya (C.) wrote:
> 
> > This patch replaces kzalloc and copy_from_user with memdup_user call
> > This change was detected with coccinelle tool
> >
> > Signed-off-by: Chaitanya Dhere <cvijaydh@...teon.com>
> > ---
> >  drivers/staging/lustre/lustre/llite/file.c |   11 +++--------
> >  1 file changed, 3 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/staging/lustre/lustre/llite/file.c b/drivers/staging/lustre/lustre/llite/file.c
> > index 85e74d1..85b5567 100644
> > --- a/drivers/staging/lustre/lustre/llite/file.c
> > +++ b/drivers/staging/lustre/lustre/llite/file.c
> > @@ -2368,14 +2368,9 @@ ll_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> >  		struct hsm_state_set	*hss;
> >  		int			 rc;
> >
> > -		hss = kzalloc(sizeof(*hss), GFP_NOFS);
> > -		if (!hss)
> > -			return -ENOMEM;
> > -
> > -		if (copy_from_user(hss, (char *)arg, sizeof(*hss))) {
> > -			OBD_FREE_PTR(hss);
> > -			return -EFAULT;
> > -		}
> > +		hss = memdup_user((char *)arg, sizeof(*hss));
> 
> memdup_user will use the flag GFP_KERNEL, ie (__GFP_WAIT | __GFP_IO |
> __GFP_FS), rather than the flag GFP_NOFS, ie (__GFP_WAIT | __GFP_IO), that
> is specified.  I don't know if this is a problem here.

Yes, this is a filesystem, so this can't be changed, as we can't have
the allocation go out and ask for more filesystem accesses in the middle
of trying to do a filesystem access :)

thanks,

greg k-h
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