Subject: [PATCH v4] arm64: fix the overlap between the kernel image and vmalloc address

From: [email-masked] (zhong jiang)
Date: Wed, 17 May 2017 11:17:51 +0800

Hi, Ard

Thank you for reply.
On 2017/5/16 23:03, Ard Biesheuvel wrote:
> On 16 May 2017 at 15:15, zhongjiang <[email-masked]> 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]>
>> Reviewed-by: Laura Abbott <[email-masked]>
>> ---
>>  arch/arm64/mm/mmu.c     |  2 +-
>>  include/linux/vmalloc.h |  1 +
>>  mm/vmalloc.c            | 34 +++++++++++++++++++++++++++-------
>>  3 files changed, 29 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 */
> Is it necessary to define this for all architectures? The VM_
> namespace explicitly declares a subrange as having architecture scope
> iirc
 It is not necessary, but more general if it is not strictly limited. As other arch
 do not care about the flags. if you go against the way. the following whethor let
 you satisfy or not.

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 3d9d786..f534df6 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -16,6 +16,13 @@
 #define VM_ALLOC               0x00000002      /* vmalloc() */
 #define VM_MAP                 0x00000004      /* vmap()ed pages */
 #define VM_USERMAP             0x00000008      /* suitable for remap_vmalloc_range */
+
+#ifdef CONFIG_ARM64
+#define VM_KERNEL              0x00000010
+#else
+#define VM_KERNEL              0
+#endif
+

 how about the above change ?
>>  #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..b456803 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -1967,11 +1967,27 @@ void *vmalloc_32_user(unsigned long size)
>>  EXPORT_SYMBOL(vmalloc_32_user);
>>
>>  /*
>> + * VM_KERNEL indicates an address is mapped linearly.The linear mapping may
>> + * use larger pages which vmalloc_to_page cannot handle.
> Please don't overload 'linear mapping' . We often refer to the direct
> kernel mapping mapping of DRAM as 'linear mapping', but in this
> context, it is not clear at all what 'linear' means.
 hmm, Exactly clear. but I will drop the comments. It is just a helper function.
 It is no necessary to add comments as Laura suggestions.
>  
>> + */
>> +static inline struct page *aligned_get_page(char *addr, struct vm_struct *vm)
> This function needs a better name
 hmm, straightforward. addr_to_page(). how about this?

 Thanks
 zhongjiang
>
>> +{
>> +       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 +1999,7 @@ 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 +2026,8 @@ 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 +2039,7 @@ 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 +2126,7 @@ 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 +2207,7 @@ 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 +2727,9 @@ 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");
>>
>> --
>> 1.7.12.4
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> .
>