Subject: [PATCH v3] arm64: fix the overlap between the kernel image and vmalloc address

From: [email-masked] (zhong jiang)
Date: Tue, 16 May 2017 22:06:18 +0800

On 2017/5/16 8:02, Laura Abbott wrote:
> On 05/10/2017 01:55 AM, Catalin Marinas wrote:
>> Given that there are a lot more mm changes than arm64, cc'ing linux-mm
>> as well.
>>
>> Patch below:
>>
>> On Wed, May 10, 2017 at 11:37:20AM +0800, zhongjiang wrote:
>>> Recently, xiaojun report the following issue.
>>>
>>> [ 4544.984139] Unable to handle kernel paging request at virtual address ffff804392800000
>>> [ 4544.991995] pgd = ffff80096745f000
>>> [ 4544.995369] [ffff804392800000] *pgd=0000000000000000
>>> [ 4545.000297] Internal error: Oops: 96000005 [#1] PREEMPT SMP
>>> [ 4545.005815] Modules linked in:
>>> [ 4545.008843] CPU: 1 PID: 8976 Comm: cat Not tainted 4.11.0-rc6 #1
>>> [ 4545.014790] Hardware name: ARM Juno development board (r1) (DT)
>>> [ 4545.020653] task: ffff8009753fdb00 task.stack: ffff80097533c000
>>> [ 4545.026520] PC is at __memcpy+0x100/0x180
>>> [ 4545.030491] LR is at vread+0x144/0x280
>>> [ 4545.034202] pc : [<ffff0000083a1000>] lr : [<ffff0000081c126c>] pstate: 20000145
>>> [ 4545.041530] sp : ffff80097533fcb0
>>> [ 4545.044811] x29: ffff80097533fcb0 x28: ffff800962d24000
>>> [ 4545.050074] x27: 0000000000001000 x26: ffff8009753fdb00
>>> [ 4545.055337] x25: ffff000008200000 x24: ffff800977801380
>>> [ 4545.060600] x23: ffff8009753fdb00 x22: ffff800962d24000
>>> [ 4545.065863] x21: 0000000000001000 x20: ffff000008200000
>>> [ 4545.071125] x19: 0000000000001000 x18: 0000ffffefa323c0
>>> [ 4545.076387] x17: 0000ffffa9c87440 x16: ffff0000081fdfd0
>>> [ 4545.081649] x15: 0000ffffa9d01588 x14: 72a77346b2407be7
>>> [ 4545.086911] x13: 5299400690000000 x12: b0000001f9001a79
>>> [ 4545.092173] x11: 97fc098d91042260 x10: 0000000000000000
>>> [ 4545.097435] x9 : 0000000000000000 x8 : 9110626091260021
>>> [ 4545.102698] x7 : 0000000000001000 x6 : ffff800962d24000
>>> [ 4545.107960] x5 : ffff8009778013b0 x4 : 0000000000000000
>>> [ 4545.113222] x3 : 0400000000000001 x2 : 0000000000000f80
>>> [ 4545.118484] x1 : ffff804392800000 x0 : ffff800962d24000
>>> [ 4545.123745]
>>> [ 4545.125220] Process cat (pid: 8976, stack limit = 0xffff80097533c000)
>>> [ 4545.131598] Stack: (0xffff80097533fcb0 to 0xffff800975340000)
>>> [ 4545.137289] fca0:                                   ffff80097533fd30 ffff000008270f64
>>> [ 4545.145049] fcc0: 000000000000e000 000000003956f000 ffff000008f950d0 ffff80097533feb8
>>> [ 4545.152809] fce0: 0000000000002000 ffff8009753fdb00 ffff800962d24000 ffff000008e8d3d8
>>> [ 4545.160568] fd00: 0000000000001000 ffff000008200000 0000000000001000 ffff800962d24000
>>> [ 4545.168327] fd20: 0000000000001000 ffff000008e884a0 ffff80097533fdb0 ffff00000826340c
>>> [ 4545.176086] fd40: ffff800976bf2800 fffffffffffffffb 000000003956d000 ffff80097533feb8
>>> [ 4545.183846] fd60: 0000000060000000 0000000000000015 0000000000000124 000000000000003f
>>> [ 4545.191605] fd80: ffff000008962000 ffff8009753fdb00 ffff8009753fdb00 ffff8009753fdb00
>>> [ 4545.199364] fda0: 0000000300000124 0000000000002000 ffff80097533fdd0 ffff0000081fb83c
>>> [ 4545.207123] fdc0: 0000000000010000 ffff80097514f900 ffff80097533fe50 ffff0000081fcb28
>>> [ 4545.214883] fde0: 0000000000010000 ffff80097514f900 0000000000000000 0000000000000000
>>> [ 4545.222642] fe00: ffff80097533fe30 ffff0000081fca1c ffff80097514f900 0000000000000000
>>> [ 4545.230401] fe20: 000000003956d000 ffff80097533feb8 ffff80097533fe50 ffff0000081fcb04
>>> [ 4545.238160] fe40: 0000000000010000 ffff80097514f900 ffff80097533fe80 ffff0000081fe014
>>> [ 4545.245919] fe60: ffff80097514f900 ffff80097514f900 000000003956d000 0000000000010000
>>> [ 4545.253678] fe80: 0000000000000000 ffff000008082f30 0000000000000000 0000800977146000
>>> [ 4545.261438] fea0: ffffffffffffffff 0000ffffa9c8745c 0000000000000124 0000000008202000
>>> [ 4545.269197] fec0: 0000000000000003 000000003956d000 0000000000010000 0000000000000000
>>> [ 4545.276956] fee0: 0000000000011011 0000000000000001 0000000000000011 0000000000000002
>>> [ 4545.284715] ff00: 000000000000003f 1f3c201f7372686b 00000000ffffffff 0000000000000030
>>> [ 4545.292474] ff20: 0000000000000038 0000000000000000 0000ffffa9bcca94 0000ffffa9d01588
>>> [ 4545.300233] ff40: 0000000000000000 0000ffffa9c87440 0000ffffefa323c0 0000000000010000
>>> [ 4545.307993] ff60: 000000000041a310 000000003956d000 0000000000000003 000000007fffe000
>>> [ 4545.315751] ff80: 00000000004088d0 0000000000010000 0000000000000000 0000000000000000
>>> [ 4545.323511] ffa0: 0000000000010000 0000ffffefa32690 0000000000404dcc 0000ffffefa32690
>>> [ 4545.331270] ffc0: 0000ffffa9c8745c 0000000060000000 0000000000000003 000000000000003f
>>> [ 4545.339029] ffe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>>> [ 4545.346786] Call trace:
>>> [ 4545.349207] Exception stack(0xffff80097533fae0 to 0xffff80097533fc10)
>>> [ 4545.355586] fae0: 0000000000001000 0001000000000000 ffff80097533fcb0 ffff0000083a1000
>>> [ 4545.363345] fb00: 000000003957c000 ffff80097533fc00 0000000020000145 0000000000000025
>>> [ 4545.371105] fb20: ffff800962d24000 ffff000008e8d3d8 0000000000001000 ffff8009753fdb00
>>> [ 4545.378864] fb40: 0000000000000000 0000000000000002 ffff80097533fd30 ffff000008082604
>>> [ 4545.386623] fb60: 0000000000001000 0001000000000000 ffff80097533fd30 ffff0000083a0a90
>>> [ 4545.394382] fb80: ffff800962d24000 ffff804392800000 0000000000000f80 0400000000000001
>>> [ 4545.402140] fba0: 0000000000000000 ffff8009778013b0 ffff800962d24000 0000000000001000
>>> [ 4545.409899] fbc0: 9110626091260021 0000000000000000 0000000000000000 97fc098d91042260
>>> [ 4545.417658] fbe0: b0000001f9001a79 5299400690000000 72a77346b2407be7 0000ffffa9d01588
>>> [ 4545.425416] fc00: ffff0000081fdfd0 0000ffffa9c87440
>>> [ 4545.430248] [<ffff0000083a1000>] __memcpy+0x100/0x180
>>> [ 4545.435253] [<ffff000008270f64>] read_kcore+0x21c/0x3b0
>>> [ 4545.440429] [<ffff00000826340c>] proc_reg_read+0x64/0x90
>>> [ 4545.445691] [<ffff0000081fb83c>] __vfs_read+0x1c/0x108
>>> [ 4545.450779] [<ffff0000081fcb28>] vfs_read+0x80/0x130
>>> [ 4545.455696] [<ffff0000081fe014>] SyS_read+0x44/0xa0
>>> [ 4545.460528] [<ffff000008082f30>] el0_svc_naked+0x24/0x28
>>> [ 4545.465790] Code: d503201f d503201f d503201f d503201f (a8c12027)
>>> [ 4545.471852] ---[ end trace 4d1897f94759f461 ]---
>>> [ 4545.476435] note: cat[8976] exited with preempt_count 2
>>>
>>> I find the issue is introduced when applying commit f9040773b7bb
>>> ("arm64: move kernel image to base of vmalloc area"). This patch
>>> make the kernel image overlap with vmalloc area. It will result in
>>> vmalloc area have the huge page table. but the vmalloc_to_page is
>>> not realize the change. and the function is public to any arch.
>>>
>>> I fix it by adding the another kernel image condition in vmalloc_to_page
>>> to make it keep the accordance with previous vmalloc mapping.
>>>
>>> Fixes: f9040773b7bb ("arm64: move kernel image to base of vmalloc area")
>>> Reported-by: tan xiaojun <[email-masked]>
>>> Signed-off-by: zhongjiang <[email-masked]>
>>> ---
>>>  arch/arm64/mm/mmu.c     |  2 +-
>>>  include/linux/vmalloc.h |  1 +
>>>  mm/vmalloc.c            | 35 ++++++++++++++++++++++++++++-------
>>>  3 files changed, 30 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>>> index 0c429ec..2265c39 100644
>>> --- a/arch/arm64/mm/mmu.c
>>> +++ b/arch/arm64/mm/mmu.c
>>> @@ -509,7 +509,7 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
>>>  	vma->addr	= va_start;
>>>  	vma->phys_addr	= pa_start;
>>>  	vma->size	= size;
>>> -	vma->flags	= VM_MAP;
>>> +	vma->flags	= VM_KERNEL;
>>>  	vma->caller	= __builtin_return_address(0);
>>>  
>>>  	vm_area_add_early(vma);
>>> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
>>> index 0328ce0..c9245af 100644
>>> --- a/include/linux/vmalloc.h
>>> +++ b/include/linux/vmalloc.h
>>> @@ -17,6 +17,7 @@
>>>  #define VM_ALLOC		0x00000002	/* vmalloc() */
>>>  #define VM_MAP			0x00000004	/* vmap()ed pages */
>>>  #define VM_USERMAP		0x00000008	/* suitable for remap_vmalloc_range */
>>> +#define VM_KERNEL		0x00000010	/* kernel pages */>>  #define VM_UNINITIALIZED	0x00000020	/* vm_struct is not fully initialized */
>>>  #define VM_NO_GUARD		0x00000040      /* don't add guard page */
>>>  #define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
>>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>>> index 1dda6d8..601d940 100644
>>> --- a/mm/vmalloc.c
>>> +++ b/mm/vmalloc.c
>>> @@ -1967,11 +1967,28 @@ void *vmalloc_32_user(unsigned long size)
>>>  EXPORT_SYMBOL(vmalloc_32_user);
>>>  
>>>  /*
>>> + * kernel image overlap with the valloc area in arm64,it
>>> + * will make the huge talbe page existence, if we walk the
>>> + * all page talbe, it may be result in the panic.
>>> + */
> I don't think we really need this comment. If you really want something here:
>
> /*
>  * VM_KERNEL indicates an address is mapped linearly. The linear mapping may
>  * use larger pages which vmalloc_to_page cannot handle.
>  */
 looks good. I will take this in next version.
>>> +static inline struct page *aligned_get_page(char *addr, struct vm_struct *vm)
>>> +{
>>> +	struct page *p = NULL;
>>> +
>>> +	if (vm->flags & VM_KERNEL)
>>> +		p = virt_to_page(lm_alias(addr));
>>> +	else
>>> +		p = vmalloc_to_page(addr);
>>> +
>>> +	return p;
>>> +}
>>> +
>>> +/*
>>>   * small helper routine , copy contents to buf from addr.
>>>   * If the page is not present, fill zero.
>>>   */
>>> -
>>> -static int aligned_vread(char *buf, char *addr, unsigned long count)
>>> +static int aligned_vread(char *buf, char *addr, unsigned long count,
>>> +					struct vm_struct *vm)
>>>  {
>>>  	struct page *p;
>>>  	int copied = 0;
>>> @@ -1983,7 +2000,7 @@ static int aligned_vread(char *buf, char *addr, unsigned long count)
>>>  		length = PAGE_SIZE - offset;
>>>  		if (length > count)
>>>  			length = count;
>>> -		p = vmalloc_to_page(addr);
>>> +		p = aligned_get_page(addr, vm);
>>>  		/*
>>>  		 * To do safe access to this _mapped_ area, we need
>>>  		 * lock. But adding lock here means that we need to add
>>> @@ -2010,7 +2027,8 @@ static int aligned_vread(char *buf, char *addr, unsigned long count)
>>>  	return copied;
>>>  }
>>>  
>>> -static int aligned_vwrite(char *buf, char *addr, unsigned long count)
>>> +static int aligned_vwrite(char *buf, char *addr, unsigned long count,
>>> +					struct vm_struct *vm)
>>>  {
>>>  	struct page *p;
>>>  	int copied = 0;
>>> @@ -2022,7 +2040,7 @@ static int aligned_vwrite(char *buf, char *addr, unsigned long count)
>>>  		length = PAGE_SIZE - offset;
>>>  		if (length > count)
>>>  			length = count;
>>> -		p = vmalloc_to_page(addr);
>>> +		p = aligned_get_page(addr, vm);
>>>  		/*
>>>  		 * To do safe access to this _mapped_ area, we need
>>>  		 * lock. But adding lock here means that we need to add
>>> @@ -2109,7 +2127,7 @@ long vread(char *buf, char *addr, unsigned long count)
>>>  		if (n > count)
>>>  			n = count;
>>>  		if (!(vm->flags & VM_IOREMAP))
>>> -			aligned_vread(buf, addr, n);
>>> +			aligned_vread(buf, addr, n, vm);
>>>  		else /* IOREMAP area is treated as memory hole */
>>>  			memset(buf, 0, n);
>>>  		buf += n;
>>> @@ -2190,7 +2208,7 @@ long vwrite(char *buf, char *addr, unsigned long count)
>>>  		if (n > count)
>>>  			n = count;
>>>  		if (!(vm->flags & VM_IOREMAP)) {
>>> -			aligned_vwrite(buf, addr, n);
>>> +			aligned_vwrite(buf, addr, n, vm);
>>>  			copied++;
>>>  		}
>>>  		buf += n;
>>> @@ -2710,6 +2728,9 @@ static int s_show(struct seq_file *m, void *p)
>>>  	if (v->flags & VM_USERMAP)
>>>  		seq_puts(m, " user");
>>>  
>>> +	if (v->flags & VM_KERNEL)
>>> +		seq_puts(m, " kernel");
>>> +
>>>  	if (is_vmalloc_addr(v->pages))
>>>  		seq_puts(m, " vpages");
>>>  
> Marking the range as being kernel pages is certainly an improvement although
> I still have mixed feelings about is_vmalloc_addr returning true for a
> region where vmalloc_to_page will not return the correct address. I also
> don't have a better idea other than complicating is_vmalloc_addr so FWIW
 yes, it is unfortunate. but we still need to handle this.
> Reviewed-by: Laura Abbott <[email-masked]>
 Thank a lot.

 Thanks
 zhongjiang
> Thanks,
> Laura
> .