From: Greg Kroah-Hartman Date: Mon, 27 Nov 2017 08:34:01 +0000 (+0100) Subject: 4.9-stable patches X-Git-Tag: v3.18.85~52 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3aeb3f20c9bcd1b1f54eb1e26ff4d741024d1141;p=thirdparty%2Fkernel%2Fstable-queue.git 4.9-stable patches added patches: x86-mm-fix-use-after-free-of-vma-during-userfaultfd-fault.patch --- diff --git a/queue-4.9/series b/queue-4.9/series index aa891834fe8..20d62811d25 100644 --- a/queue-4.9/series +++ b/queue-4.9/series @@ -3,3 +3,4 @@ s390-runtime-instrumention-fix-possible-memory-corruption.patch s390-disassembler-add-missing-end-marker-for-e7-table.patch s390-disassembler-increase-show_code-buffer-size.patch acpi-ec-fix-regression-related-to-triggering-source-of-ec-event-handling.patch +x86-mm-fix-use-after-free-of-vma-during-userfaultfd-fault.patch diff --git a/queue-4.9/x86-mm-fix-use-after-free-of-vma-during-userfaultfd-fault.patch b/queue-4.9/x86-mm-fix-use-after-free-of-vma-during-userfaultfd-fault.patch new file mode 100644 index 00000000000..2807708dc72 --- /dev/null +++ b/queue-4.9/x86-mm-fix-use-after-free-of-vma-during-userfaultfd-fault.patch @@ -0,0 +1,80 @@ +From cb0631fd3cf9e989cd48293fe631cbc402aec9a9 Mon Sep 17 00:00:00 2001 +From: Vlastimil Babka +Date: Wed, 1 Nov 2017 08:21:25 +0100 +Subject: x86/mm: fix use-after-free of vma during userfaultfd fault + +From: Vlastimil Babka + +commit cb0631fd3cf9e989cd48293fe631cbc402aec9a9 upstream. + +Syzkaller with KASAN has reported a use-after-free of vma->vm_flags in +__do_page_fault() with the following reproducer: + + mmap(&(0x7f0000000000/0xfff000)=nil, 0xfff000, 0x3, 0x32, 0xffffffffffffffff, 0x0) + mmap(&(0x7f0000011000/0x3000)=nil, 0x3000, 0x1, 0x32, 0xffffffffffffffff, 0x0) + r0 = userfaultfd(0x0) + ioctl$UFFDIO_API(r0, 0xc018aa3f, &(0x7f0000002000-0x18)={0xaa, 0x0, 0x0}) + ioctl$UFFDIO_REGISTER(r0, 0xc020aa00, &(0x7f0000019000)={{&(0x7f0000012000/0x2000)=nil, 0x2000}, 0x1, 0x0}) + r1 = gettid() + syz_open_dev$evdev(&(0x7f0000013000-0x12)="2f6465762f696e7075742f6576656e742300", 0x0, 0x0) + tkill(r1, 0x7) + +The vma should be pinned by mmap_sem, but handle_userfault() might (in a +return to userspace scenario) release it and then acquire again, so when +we return to __do_page_fault() (with other result than VM_FAULT_RETRY), +the vma might be gone. + +Specifically, per Andrea the scenario is + "A return to userland to repeat the page fault later with a + VM_FAULT_NOPAGE retval (potentially after handling any pending signal + during the return to userland). The return to userland is identified + whenever FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in + vmf->flags" + +However, since commit a3c4fb7c9c2e ("x86/mm: Fix fault error path using +unsafe vma pointer") there is a vma_pkey() read of vma->vm_flags after +that point, which can thus become use-after-free. Fix this by moving +the read before calling handle_mm_fault(). + +Reported-by: syzbot +Reported-by: Dmitry Vyukov +Suggested-by: Kirill A. Shutemov +Fixes: 3c4fb7c9c2e ("x86/mm: Fix fault error path using unsafe vma pointer") +Reviewed-by: Andrea Arcangeli +Signed-off-by: Vlastimil Babka +Signed-off-by: Linus Torvalds +Cc: Eric Biggers +Signed-off-by: Greg Kroah-Hartman + +--- + arch/x86/mm/fault.c | 11 ++++++++++- + 1 file changed, 10 insertions(+), 1 deletion(-) + +--- a/arch/x86/mm/fault.c ++++ b/arch/x86/mm/fault.c +@@ -1393,7 +1393,17 @@ good_area: + * make sure we exit gracefully rather than endlessly redo + * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if + * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. ++ * ++ * Note that handle_userfault() may also release and reacquire mmap_sem ++ * (and not return with VM_FAULT_RETRY), when returning to userland to ++ * repeat the page fault later with a VM_FAULT_NOPAGE retval ++ * (potentially after handling any pending signal during the return to ++ * userland). The return to userland is identified whenever ++ * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. ++ * Thus we have to be careful about not touching vma after handling the ++ * fault, so we read the pkey beforehand. + */ ++ pkey = vma_pkey(vma); + fault = handle_mm_fault(vma, address, flags); + major |= fault & VM_FAULT_MAJOR; + +@@ -1420,7 +1430,6 @@ good_area: + return; + } + +- pkey = vma_pkey(vma); + up_read(&mm->mmap_sem); + if (unlikely(fault & VM_FAULT_ERROR)) { + mm_fault_error(regs, error_code, address, &pkey, fault);