lkml.org 
[lkml]   [2021]   [Oct]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
From
Date
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

\
 
 \ /
  Last update: 2021-10-08 12:47    [from the cache]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and my Meterkast|Read the blog