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: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Pine.LNX.4.64.0911021222010.32400@sister.anvils>
Date:	Mon, 2 Nov 2009 12:31:39 +0000 (GMT)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	Jiri Slaby <jirislaby@...il.com>
cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/1] MM: swapfile, fix crash on double swapon

On Mon, 2 Nov 2009, Jiri Slaby wrote:

> Double swapon on a device causes a crash:
> BUG: unable to handle kernel NULL pointer dereference at (null)

Thanks a lot for finding that: it doesn't just happen with a double
swapon of the same device, it happens with most kinds of error in
the swapon sequence.  I thought I was being nice and tidy moving
that initialization, but actually I was just being careless.

> IP: [<ffffffff810af160>] sys_swapon+0x1f0/0xc60
> PGD 1dc0b067 PUD 1dc09067 PMD 0
> Oops: 0000 [#1] SMP
> last sysfs file:
> CPU 1
> Modules linked in:
> Pid: 562, comm: swapon Tainted: G        W  2.6.32-rc5-mm1_64 #867
> RIP: 0010:[<ffffffff810af160>]  [<ffffffff810af160>] sys_swapon+0x1f0/0xc60
> ...
> 
> It is due to swap_info_struct->first_swap_extent.list not being
> initialized. ->next is NULL in such a situation and
> destroy_swap_extents fails to iterate over the list with the BUG
> above.
> 
> Introduced by swap_info-include-first_swap_extent.patch. Revert the
> INIT_LIST_HEAD move.
> 
> Signed-off-by: Jiri Slaby <jirislaby@...il.com>
> Cc: Hugh Dickins <hugh.dickins@...cali.co.uk>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Rik van Riel <riel@...hat.com>

Acked-by: Hugh Dickins <hugh.dickins@...cali.co.uk>

> ---
>  mm/swapfile.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 93e71cf..26ef6a2 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1313,7 +1313,6 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
>  	if (start_page == 0) {
>  		se = &sis->first_swap_extent;
>  		sis->curr_swap_extent = se;
> -		INIT_LIST_HEAD(&se->list);
>  		se->start_page = 0;
>  		se->nr_pages = nr_pages;
>  		se->start_block = start_block;
> @@ -1769,6 +1768,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>  		kfree(p);
>  		goto out;
>  	}
> +	INIT_LIST_HEAD(&p->first_swap_extent.list);
>  	if (type >= nr_swapfiles) {
>  		p->type = type;
>  		swap_info[type] = p;
> -- 
> 1.6.4.2
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ