Re: [PATCH] mm/mempolicy: fix !vma in new_vma_page()

[Bob Liu]

On 12/17/2013 02:44 PM, Wanpeng Li wrote:
> BUG_ON(!vma) assumption is introduced by commit 0bf598d8 (mbind: add BUG_ON(!vma) 
> in new_vma_page()), however, even if address = __vma_address(page, vma); and 
> vma->start < address < vma->end; page_address_in_vma() may still return -EFAULT 
> because of many other conditions in it. As a result the while loop in new_vma_page() 
> may end with vma=NULL. This patch revert the commit and also fix the potential 
> dereference NULL pointer by Dan. http://marc.info/?l=linux-mm&m=137689530323257&w=2
> 
> kernel BUG at mm/mempolicy.c:1204!
> invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> CPU: 3 PID: 7056 Comm: trinity-child3 Not tainted 3.13.0-rc3+ #2
> task: ffff8801ca5295d0 ti: ffff88005ab20000 task.ti: ffff88005ab20000
> RIP: 0010:[<ffffffff8119f200>]  [<ffffffff8119f200>] new_vma_page+0x70/0x90
> RSP: 0000:ffff88005ab21db0  EFLAGS: 00010246
> RAX: fffffffffffffff2 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000008040075 RSI: ffff8801c3d74600 RDI: ffffea00079a8b80
> RBP: ffff88005ab21dc8 R08: 0000000000000004 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: fffffffffffffff2
> R13: ffffea00079a8b80 R14: 0000000000400000 R15: 0000000000400000
> 
> FS:  00007ff49c6f4740(0000) GS:ffff880244e00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ff49c68f994 CR3: 000000005a205000 CR4: 00000000001407e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Stack:
>  ffffea00079a8b80 ffffea00079a8bc0 ffffea00079a8ba0 ffff88005ab21e50
>  ffffffff811adc7a 0000000000000000 ffff8801ca5295d0 0000000464e224f8
>  0000000000000000 0000000000000002 0000000000000000 ffff88020ce75c00
> Call Trace:
>  [<ffffffff811adc7a>] migrate_pages+0x12a/0x850
>  [<ffffffff8119f190>] ? alloc_pages_vma+0x1b0/0x1b0
>  [<ffffffff8119fa13>] SYSC_mbind+0x513/0x6a0
>  [<ffffffff810aa7de>] ? lock_release_holdtime.part.29+0xee/0x170
>  [<ffffffff8119fbae>] SyS_mbind+0xe/0x10
>  [<ffffffff817626a9>] ia32_do_call+0x13/0x13
> Code: 85 c0 75 2f 4c 89 e1 48 89 da 31 f6 bf da 00 02 00 65 44 8b 04 25 08 f7 1c 00 e8 ec fd ff ff 5b 41 5c 41 5d 5d c3 0f 1f 44 00 00 <0f> 0b 66 0f 1f 44 00
> +00 4c 89 e6 48 89 df ba 01 00 00 00 e8 48
> RIP  [<ffffffff8119f200>] new_vma_page+0x70/0x90
>  RSP <ffff88005ab21db0>
> 
> Reported-by: Dave Jones <davej@xxxxxxxxxx>
> Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>

Reviewed-by: Bob Liu <bob.liu@xxxxxxxxxx>

> ---
>  mm/mempolicy.c |   14 ++++++++------
>  1 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index eca4a31..7247c38 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1197,14 +1197,16 @@ static struct page *new_vma_page(struct page *page, unsigned long private, int *
>  			break;
>  		vma = vma->vm_next;
>  	}
> +
> +	if (PageHuge(page)) {
> +		if (vma)
> +			return alloc_huge_page_noerr(vma, address, 1);
> +		else
> +			return NULL;
> +	}
>  	/*
> -	 * queue_pages_range() confirms that @page belongs to some vma,
> -	 * so vma shouldn't be NULL.
> +	 * if !vma, alloc_page_vma() will use task or system default policy
>  	 */
> -	BUG_ON(!vma);
> -
> -	if (PageHuge(page))
> -		return alloc_huge_page_noerr(vma, address, 1);
>  	return alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
>  }
>  #else
> 

-- 
Regards,
-Bob
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