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
Link: http://lkml.kernel.org/r/151130418681.4029.7118245855057952010.stgit@dwillia... Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Signed-off-by: Dan Williams dan.j.williams@intel.com Reported-by: Jeff Moyer jmoyer@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- drivers/dax/dax.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c index 40be3747724d..473b44c008dd 100644 --- a/drivers/dax/dax.c +++ b/drivers/dax/dax.c @@ -453,9 +453,21 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr, return rc; }
+static int dax_dev_split(struct vm_area_struct *vma, unsigned long addr) +{ + struct file *filp = vma->vm_file; + struct dax_dev *dax_dev = filp->private_data; + struct dax_region *dax_region = dax_dev->region; + + if (!IS_ALIGNED(addr, dax_region->align)) + return -EINVAL; + return 0; +} + static const struct vm_operations_struct dax_dev_vm_ops = { .fault = dax_dev_fault, .pmd_fault = dax_dev_pmd_fault, + .split = dax_dev_split, };
static int dax_mmap(struct file *filp, struct vm_area_struct *vma)