The patch titled Subject: mm/secretmem: Fix NULL page->mapping dereference in page_is_secretmem() has been added to the -mm tree. Its filename is mm-fix-null-page-mapping-dereference-in-page_is_secretmem.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-fix-null-page-mapping-dereference-in-page_is_secretmem.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-null-page-mapping-dereference-in-page_is_secretmem.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Sean Christopherson <seanjc@xxxxxxxxxx> Subject: mm/secretmem: Fix NULL page->mapping dereference in page_is_secretmem() 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 Link: https://lkml.kernel.org/r/20211007231502.3552715-1-seanjc@xxxxxxxxxx Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas") Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Reported-by: Darrick J. Wong <djwong@xxxxxxxxxx> Reported-by: Stephen <stephenackerman16@xxxxxxxxx> Tested-by: Darrick J. Wong <djwong@xxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/secretmem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/secretmem.h~mm-fix-null-page-mapping-dereference-in-page_is_secretmem +++ a/include/linux/secretmem.h @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(str 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; _ Patches currently in -mm which might be from seanjc@xxxxxxxxxx are mm-fix-null-page-mapping-dereference-in-page_is_secretmem.patch