Patch "device-dax: implement ->split() to catch invalid munmap attempts" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

    device-dax: implement ->split() to catch invalid munmap attempts

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
device-dax-implement-split-to-catch-invalid-munmap-attempts.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dan Williams <[email protected]>
Date: Wed, 29 Nov 2017 16:10:32 -0800
Subject: device-dax: implement ->split() to catch invalid munmap attempts

From: Dan Williams <[email protected]>

commit 9702cffdbf2129516db679e4467db81e1cd287da upstream.

Similar to how device-dax enforces that the 'address', 'offset', and 'len' parameters to mmap() be aligned to the device's fundamental alignment, the same constraints apply to munmap(). Implement ->split() to fail munmap calls that violate the alignment constraint.

Otherwise, we later fail VM_BUG_ON checks in the unmap_page_range() path with crash signatures of the form:

    vma ffff8800b60c8a88 start 00007f88c0000000 end 00007f88c0e00000
    next           (null) prev           (null) mm ffff8800b61150c0
    prot 8000000000000027 anon_vma           (null) vm_ops ffffffffa0091240
    pgoff 0 file ffff8800b638ef80 private_data           (null)
    flags: 0x380000fb(read|write|shared|mayread|maywrite|mayexec|mayshare|softdirty|mixedmap|hugepage)
    ------------[ cut here ]------------
    kernel BUG at mm/huge_memory.c:2014!
    [..]
    RIP: 0010:__split_huge_pud+0x12a/0x180
    [..]
    Call Trace:
     unmap_page_range+0x245/0xa40
     ? __vma_adjust+0x301/0x990
     unmap_vmas+0x4c/0xa0
     unmap_region+0xae/0x120
     ? __vma_rb_erase+0x11a/0x230
     do_munmap+0x276/0x410
     vm_munmap+0x6a/0xa0
     SyS_munmap+0x1d/0x30

---
 drivers/dax/device.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

@@ -427,9 +427,21 @@ static int dev_dax_fault(struct vm_fault
 	return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
 }
 
+static int dev_dax_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	struct file *filp = vma->vm_file;
+	struct dev_dax *dev_dax = filp->private_data;
+	struct dax_region *dax_region = dev_dax->region;
+
+	if (!IS_ALIGNED(addr, dax_region->align))
+		return -EINVAL;
+	return 0;
+}
+
 static const struct vm_operations_struct dax_vm_ops = {
 	.fault = dev_dax_fault,
 	.huge_fault = dev_dax_huge_fault,
+	.split = dev_dax_split,
 };
 
 static int dax_mmap(struct file *filp, struct vm_area_struct *vma)

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch queue-4.14/ib-core-disable-memory-registration-of-filesystem-dax-vmas.patch queue-4.14/mm-introduce-get_user_pages_longterm.patch queue-4.14/mm-fail-get_vaddr_frames-for-filesystem-dax-mappings.patch queue-4.14/device-dax-implement-split-to-catch-invalid-munmap-attempts.patch queue-4.14/v4l2-disable-filesystem-dax-mapping-support.patch queue-4.14/mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages.patch queue-4.14/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch