From 3cfd22be0ad663248fadfc8f6ffa3e255c394552 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Fri, 28 Dec 2018 00:38:47 -0800 Subject: [PATCH] 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 Reviewed-by: Andrea Arcangeli Acked-by: Mike Rapoport Reviewed-by: William Kucharski Cc: Andrea Arcangeli Cc: Mike Rapoport Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Pavel Emelyanov Cc: Pravin Shedge Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index e211b99d33c4..89800fc7dc9d 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -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); } }