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* [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
@ 2021-10-07 23:15 Sean Christopherson
  2021-10-08 10:46 ` David Hildenbrand
  2021-10-10  5:29 ` Mike Rapoport
  0 siblings, 2 replies; 4+ messages in thread
From: Sean Christopherson @ 2021-10-07 23:15 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-kernel, Mike Rapoport, linux-mm, Darrick J . Wong, Stephen,
	Sean Christopherson

Check for a NULL page->mapping before dereferencing the mapping in
page_is_secretmem(), as the page's mapping can be nullified while gup()
is running, e.g. by reclaim or truncation.

  BUG: kernel NULL pointer dereference, address: 0000000000000068
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G        W
  RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0
  Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be
  RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046
  RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900
  ...
  CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0
  Call Trace:
   get_user_pages_fast_only+0x13/0x20
   hva_to_pfn+0xa9/0x3e0
   try_async_pf+0xa1/0x270
   direct_page_fault+0x113/0xad0
   kvm_mmu_page_fault+0x69/0x680
   vmx_handle_exit+0xe1/0x5d0
   kvm_arch_vcpu_ioctl_run+0xd81/0x1c70
   kvm_vcpu_ioctl+0x267/0x670
   __x64_sys_ioctl+0x83/0xa0
   do_syscall_64+0x56/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Cc: Mike Rapoport <rppt@kernel.org>
Cc: linux-mm@kvack.org
Reported-by: Darrick J. Wong <djwong@kernel.org>
Reported-by: Stephen <stephenackerman16@gmail.com>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 include/linux/secretmem.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
index 21c3771e6a56..988528b5da43 100644
--- a/include/linux/secretmem.h
+++ b/include/linux/secretmem.h
@@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *page)
 	mapping = (struct address_space *)
 		((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
 
-	if (mapping != page->mapping)
+	if (!mapping || mapping != page->mapping)
 		return false;
 
 	return mapping->a_ops == &secretmem_aops;
-- 
2.33.0.882.g93a45727a2-goog


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
  2021-10-07 23:15 [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem() Sean Christopherson
@ 2021-10-08 10:46 ` David Hildenbrand
  2021-10-08 14:17   ` Sean Christopherson
  2021-10-10  5:29 ` Mike Rapoport
  1 sibling, 1 reply; 4+ messages in thread
From: David Hildenbrand @ 2021-10-08 10:46 UTC (permalink / raw)
  To: Sean Christopherson, Andrew Morton
  Cc: linux-kernel, Mike Rapoport, linux-mm, Darrick J . Wong, Stephen

On 08.10.21 01:15, Sean Christopherson wrote:
> Check for a NULL page->mapping before dereferencing the mapping in
> page_is_secretmem(), as the page's mapping can be nullified while gup()
> is running, e.g. by reclaim or truncation.
> 
>    BUG: kernel NULL pointer dereference, address: 0000000000000068
>    #PF: supervisor read access in kernel mode
>    #PF: error_code(0x0000) - not-present page
>    PGD 0 P4D 0
>    Oops: 0000 [#1] PREEMPT SMP NOPTI
>    CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G        W
>    RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0
>    Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be
>    RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046
>    RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934
>    RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900
>    ...
>    CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0
>    Call Trace:
>     get_user_pages_fast_only+0x13/0x20
>     hva_to_pfn+0xa9/0x3e0
>     try_async_pf+0xa1/0x270
>     direct_page_fault+0x113/0xad0
>     kvm_mmu_page_fault+0x69/0x680
>     vmx_handle_exit+0xe1/0x5d0
>     kvm_arch_vcpu_ioctl_run+0xd81/0x1c70
>     kvm_vcpu_ioctl+0x267/0x670
>     __x64_sys_ioctl+0x83/0xa0
>     do_syscall_64+0x56/0x80
>     entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: linux-mm@kvack.org
> Reported-by: Darrick J. Wong <djwong@kernel.org>
> Reported-by: Stephen <stephenackerman16@gmail.com>
> Tested-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   include/linux/secretmem.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
> index 21c3771e6a56..988528b5da43 100644
> --- a/include/linux/secretmem.h
> +++ b/include/linux/secretmem.h
> @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *page)
>   	mapping = (struct address_space *)
>   		((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
>   
> -	if (mapping != page->mapping)
> +	if (!mapping || mapping != page->mapping)
>   		return false;
>   
>   	return mapping->a_ops == &secretmem_aops;
> 

I assume we want to add

Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
Cc: <stable@vger.kernel.org> # v5.14

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
  2021-10-08 10:46 ` David Hildenbrand
@ 2021-10-08 14:17   ` Sean Christopherson
  0 siblings, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2021-10-08 14:17 UTC (permalink / raw)
  To: David Hildenbrand
  Cc: Andrew Morton, linux-kernel, Mike Rapoport, linux-mm,
	Darrick J . Wong, Stephen

On Fri, Oct 08, 2021, David Hildenbrand wrote:
> I assume we want to add
> 
> Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas")
> Cc: <stable@vger.kernel.org> # v5.14

Doh, yes we do.  Thanks!

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
  2021-10-07 23:15 [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem() Sean Christopherson
  2021-10-08 10:46 ` David Hildenbrand
@ 2021-10-10  5:29 ` Mike Rapoport
  1 sibling, 0 replies; 4+ messages in thread
From: Mike Rapoport @ 2021-10-10  5:29 UTC (permalink / raw)
  To: Sean Christopherson
  Cc: Andrew Morton, linux-kernel, linux-mm, Darrick J . Wong, Stephen

On Thu, Oct 07, 2021 at 04:15:02PM -0700, Sean Christopherson wrote:
> Check for a NULL page->mapping before dereferencing the mapping in
> page_is_secretmem(), as the page's mapping can be nullified while gup()
> is running, e.g. by reclaim or truncation.
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000068
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 0 P4D 0
>   Oops: 0000 [#1] PREEMPT SMP NOPTI
>   CPU: 6 PID: 4173897 Comm: CPU 3/KVM Tainted: G        W
>   RIP: 0010:internal_get_user_pages_fast+0x621/0x9d0
>   Code: <48> 81 7a 68 80 08 04 bc 0f 85 21 ff ff 8 89 c7 be
>   RSP: 0018:ffffaa90087679b0 EFLAGS: 00010046
>   RAX: ffffe3f37905b900 RBX: 00007f2dd561e000 RCX: ffffe3f37905b934
>   RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffe3f37905b900
>   ...
>   CR2: 0000000000000068 CR3: 00000004c5898003 CR4: 00000000001726e0
>   Call Trace:
>    get_user_pages_fast_only+0x13/0x20
>    hva_to_pfn+0xa9/0x3e0
>    try_async_pf+0xa1/0x270
>    direct_page_fault+0x113/0xad0
>    kvm_mmu_page_fault+0x69/0x680
>    vmx_handle_exit+0xe1/0x5d0
>    kvm_arch_vcpu_ioctl_run+0xd81/0x1c70
>    kvm_vcpu_ioctl+0x267/0x670
>    __x64_sys_ioctl+0x83/0xa0
>    do_syscall_64+0x56/0x80
>    entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: linux-mm@kvack.org
> Reported-by: Darrick J. Wong <djwong@kernel.org>
> Reported-by: Stephen <stephenackerman16@gmail.com>
> Tested-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>

> ---
>  include/linux/secretmem.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
> index 21c3771e6a56..988528b5da43 100644
> --- a/include/linux/secretmem.h
> +++ b/include/linux/secretmem.h
> @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *page)
>  	mapping = (struct address_space *)
>  		((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
>  
> -	if (mapping != page->mapping)
> +	if (!mapping || mapping != page->mapping)
>  		return false;
>  
>  	return mapping->a_ops == &secretmem_aops;
> -- 
> 2.33.0.882.g93a45727a2-goog
> 

-- 
Sincerely yours,
Mike.

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-10-10  5:30 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-07 23:15 [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem() Sean Christopherson
2021-10-08 10:46 ` David Hildenbrand
2021-10-08 14:17   ` Sean Christopherson
2021-10-10  5:29 ` Mike Rapoport

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