linux-kernel - Re: [PATCH v3] vmcore: prevent PT_NOTE p

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Date:	Wed, 5 Feb 2014 11:49:52 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"Pearson, Greg" <greg.pearson@...com>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"d.hatayama@...fujitsu.com" <d.hatayama@...fujitsu.com>,
	"holzheu@...ux.vnet.ibm.com" <holzheu@...ux.vnet.ibm.com>,
	"dhowells@...hat.com" <dhowells@...hat.com>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] vmcore: prevent PT_NOTE p_memsz overflow during
 header update

On Wed, Feb 05, 2014 at 04:39:05PM +0000, Pearson, Greg wrote:
> On 02/05/2014 06:39 AM, Vivek Goyal wrote:
> > On Tue, Feb 04, 2014 at 04:25:52PM -0700, Greg Pearson wrote:
> >
> > [..]
> >> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> >> index 2ca7ba0..88d4585 100644
> >> --- a/fs/proc/vmcore.c
> >> +++ b/fs/proc/vmcore.c
> >> @@ -468,17 +468,24 @@ static int __init update_note_header_size_elf64(const Elf64_Ehdr *ehdr_ptr)
> >>   			return rc;
> >>   		}
> >>   		nhdr_ptr = notes_section;
> >> -		while (real_sz < max_sz) {
> >> -			if (nhdr_ptr->n_namesz == 0)
> >> -				break;
> >> +		while (nhdr_ptr->n_namesz != 0) {
> >>   			sz = sizeof(Elf64_Nhdr) +
> >>   				((nhdr_ptr->n_namesz + 3) & ~3) +
> >>   				((nhdr_ptr->n_descsz + 3) & ~3);
> >> +			if ((real_sz + sz) > max_sz) {
> >> +				pr_warn("Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x%x, n_descsz=0x%x\n",
> >> +					nhdr_ptr->n_namesz, nhdr_ptr->n_descsz);
> > You will need line break in pr_warn(). Too long a line. Limit it 80
> > columns per line.
> 
> The checkpatch.pl script issues a warning when you break quoted strings, 
> I have no personal preference. Just let me know if you want me to ignore 
> the checkpatch warning and conform to the 80 column per line limit.

Hmm.., I am reading CodingStyle and it does say that do not break user
visible strings as it breaks ability to grep these. 

"However, never break user-visible strings such as
printk messages, because that breaks the ability to grep for them."

Ok, so I am fine with this patch.

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Thanks
Vivek
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