Patch "userfaultfd: non-cooperative: notify about unmap of destination during mremap" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

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

    userfaultfd: non-cooperative: notify about unmap of destination during mremap

to the 4.12-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:
     userfaultfd-non-cooperative-notify-about-unmap-of-destination-during-mremap.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From b22823719302e88d0e2a6bb06433bd97b175a8d8 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Wed, 2 Aug 2017 13:31:55 -0700
Subject: userfaultfd: non-cooperative: notify about unmap of destination during mremap

From: Mike Rapoport <rppt@linux.vnet.ibm.com>

commit b22823719302e88d0e2a6bb06433bd97b175a8d8 upstream.

When mremap is called with MREMAP_FIXED it unmaps memory at the
destination address without notifying userfaultfd monitor.

If the destination were registered with userfaultfd, the monitor has no
way to distinguish between the old and new ranges and to properly relate
the page faults that would occur in the destination region.

Fixes: 897ab3e0c49e ("userfaultfd: non-cooperative: add event for memory unmaps")
Link: http://lkml.kernel.org/r/1500276876-3350-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/mremap.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -429,6 +429,7 @@ static struct vm_area_struct *vma_to_res
 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
 		unsigned long new_addr, unsigned long new_len, bool *locked,
 		struct vm_userfaultfd_ctx *uf,
+		struct list_head *uf_unmap_early,
 		struct list_head *uf_unmap)
 {
 	struct mm_struct *mm = current->mm;
@@ -447,7 +448,7 @@ static unsigned long mremap_to(unsigned
 	if (addr + old_len > new_addr && new_addr + new_len > addr)
 		goto out;
 
-	ret = do_munmap(mm, new_addr, new_len, NULL);
+	ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
 	if (ret)
 		goto out;
 
@@ -515,6 +516,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
 	unsigned long charged = 0;
 	bool locked = false;
 	struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
+	LIST_HEAD(uf_unmap_early);
 	LIST_HEAD(uf_unmap);
 
 	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
@@ -542,7 +544,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, a
 
 	if (flags & MREMAP_FIXED) {
 		ret = mremap_to(addr, old_len, new_addr, new_len,
-				&locked, &uf, &uf_unmap);
+				&locked, &uf, &uf_unmap_early, &uf_unmap);
 		goto out;
 	}
 
@@ -622,6 +624,7 @@ out:
 	up_write(&current->mm->mmap_sem);
 	if (locked && new_len > old_len)
 		mm_populate(new_addr + old_len, new_len - old_len);
+	userfaultfd_unmap_complete(mm, &uf_unmap_early);
 	mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
 	userfaultfd_unmap_complete(mm, &uf_unmap);
 	return ret;


Patches currently in stable-queue which might be from rppt@linux.vnet.ibm.com are

queue-4.12/userfaultfd-non-cooperative-flush-event_wqh-at-release-time.patch
queue-4.12/userfaultfd_zeropage-return-enospc-in-case-mm-has-gone.patch
queue-4.12/userfaultfd-non-cooperative-notify-about-unmap-of-destination-during-mremap.patch