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@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Reported-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Reported-by: Stephen <stephenackerman16@xxxxxxxxx>
Tested-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxxx> # v5.14
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
