Commit 3cfd22be authored Dec 28, 2018 by Peter Xu Committed by Linus Torvalds Dec 28, 2018

userfaultfd: clear flag if remap event not enabled

When the process being tracked does mremap() without
UFFD_FEATURE_EVENT_REMAP on the corresponding tracking uffd file handle,
we should not generate the remap event, and at the same time we should
clear all the uffd flags on the new VMA.  Without this patch, we can still
have the VM_UFFD_MISSING|VM_UFFD_WP flags on the new VMA even the fault
handling process does not even know the existance of the VMA.

Link: http://lkml.kernel.org/r/20181211053409.20317-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Pravin Shedge <pravin.shedge4linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 125b860b

fs/userfaultfd.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -735,10 +735,18 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,
		struct userfaultfd_ctx *ctx;

		ctx = vma->vm_userfaultfd_ctx.ctx;
		if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {

		if (!ctx)
		return;

		if (ctx->features & UFFD_FEATURE_EVENT_REMAP) {
		vm_ctx->ctx = ctx;
		userfaultfd_ctx_get(ctx);
		WRITE_ONCE(ctx->mmap_changing, true);
		} else {
		/* Drop uffd context if remap feature not enabled */
		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
		vma->vm_flags &= ~(VM_UFFD_WP \| VM_UFFD_MISSING);
		}
		}

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