linux-kernel - Re: [PATCH] Fix OOPS in mmap_region() when merging adjacent VM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20090202205515.EC89.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Mon,  2 Feb 2009 20:59:23 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com, Hugh Dickins <hugh@...itas.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Greg KH <gregkh@...e.de>,
	Maksim Yevmenkin <maksim.yevmenkin@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	will@...wder-design.com, Rik van Riel <riel@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mikos Szeredi <miklos@...redi.hu>
Subject: Re: [PATCH] Fix OOPS in mmap_region() when merging adjacent VM_LOCKED file segments

Hi

I went to trip for last three days and I returned today.
I suprised this loooong thread now :)

I have one comment.

> TOTALLY UNTESTED. As usual. But the concept is pretty simple, and it 
> actually removes a fair chunk of hacky code.  The only reason the diffstat 
> output says that it adds more lines than it deletes is that I added more 
> comments and made that helper inline function rather than make a complex 
> conditional.
> 
> Whaddaya think?
> 
> 		Linus
> 
> ---
>  mm/mmap.c  |   48 +++++++++++++++++++++++++-----------------------
>  mm/shmem.c |    2 +-
>  2 files changed, 26 insertions(+), 24 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index c581df1..5fcaec3 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1090,6 +1090,15 @@ int vma_wants_writenotify(struct vm_area_struct *vma)
>  		mapping_cap_account_dirty(vma->vm_file->f_mapping);
>  }
>  
> +/*
> + * We account for memory if it's a private writeable mapping,
> + * and VM_NORESERVE wasn't set.
> + */
> +static inline int private_accountable_mapping(unsigned int vm_flags)
> +{
> +	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
> +}
> +
>  unsigned long mmap_region(struct file *file, unsigned long addr,
>  			  unsigned long len, unsigned long flags,
>  			  unsigned int vm_flags, unsigned long pgoff,
> @@ -1117,23 +1126,24 @@ munmap_back:
>  	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
>  		return -ENOMEM;
>  
> -	if (flags & MAP_NORESERVE)
> +	/*
> +	 * Set 'VM_NORESERVE' if we should not account for the
> +	 * memory use of this mapping. We only honor MAP_NORESERVE
> +	 * if we're allowed to overcommit memory.
> +	 */
> +	if ((flags & MAP_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER)

I afraid this line a bit.
if following scenario happend, we can lost VM_NORESERVE?

1. admin set overcommit_memory to "never"
2. mmap
3. admin set overcommit_memory to "guess"


thanks.




--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/