From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Peter Xu , Andrea Arcangeli , Mike Rapoport , "Kirill A . Shutemov" , Hugh Dickins , Pavel Emelyanov , Pravin Shedge , Andrew Morton , Linus Torvalds , Sasha Levin , linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 96/97] userfaultfd: clear flag if remap event not enabled Date: Tue, 8 Jan 2019 14:29:45 -0500 Message-Id: <20190108192949.122407-96-sashal@kernel.org> In-Reply-To: <20190108192949.122407-1-sashal@kernel.org> References: <20190108192949.122407-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-ID: From: Peter Xu [ Upstream commit 3cfd22be0ad663248fadfc8f6ffa3e255c394552 ] 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 Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 7a85e609fc27..d8b8323e80f4 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); } } -- 2.19.1