[v2] userfaultfd: clear flag if remap event not enabled
diff mbox series

Message ID 20181211053409.20317-1-peterx@redhat.com
State In Next
Commit 3cfd22be0ad663248fadfc8f6ffa3e255c394552
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Series
  • [v2] userfaultfd: clear flag if remap event not enabled
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Commit Message

Peter Xu Dec. 11, 2018, 5:34 a.m. UTC
When the process being tracked do 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.

CC: Andrea Arcangeli <aarcange@redhat.com>
CC: Andrew Morton <akpm@linux-foundation.org>
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>
CC: linux-mm@kvack.org
CC: linux-kernel@vger.kernel.org
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 fs/userfaultfd.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

William Kucharski Dec. 11, 2018, 1:46 p.m. UTC | #1
> On Dec 10, 2018, at 10:34 PM, Peter Xu <peterx@redhat.com> wrote:
> 
> ---
> fs/userfaultfd.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..4567b5b6fd32 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -736,10 +736,18 @@ 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);
> 	}
> }
> 
> -- 
> 2.17.1
> 

Looks good.

Reviewed-by: William Kucharski <william.kucharski@oracle.com>

Patch
diff mbox series

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index cd58939dc977..4567b5b6fd32 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -736,10 +736,18 @@  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);
 	}
 }