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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>
This commit is contained in:
Peter Xu 2018-12-28 00:38:47 -08:00 committed by Linus Torvalds
parent 125b860b25
commit 3cfd22be0a
1 changed files with 9 additions and 1 deletions
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10
fs/userfaultfd.c
View File

@ -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);
}
}