lkml.org 
[lkml]   [2021]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH] mm: Fix NULL page->mapping dereference in page_is_secretmem()
    From
    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
    \
     
     \ /
      Last update: 2021-10-08 01:15    [W:3.758 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site