From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: [PATCH mm-unstable v1 04/20] mm: add early FAULT_FLAG_UNSHARE consistency checks Date: Wed, 16 Nov 2022 11:26:43 +0100 Message-ID: <20221116102659.70287-5-david@redhat.com> References: <20221116102659.70287-1-david@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=M7DNfOhrYbohUXndRqP/KN9onJ+ww6DTkvUTp40MZRc=; b=Ng/+9ZT7YIQlI2 Xt20z2KD1nPeHZVbL574Jv9V2+/9nWoSF6If7lysxR/gQwwvvCsJ+3JUuPDrh91wopA+dJLbZqpu1 daifhcZ6iufs4/IXGSZySl84SPAgtV075G1JznBbG4YdqyVqI6W/gm/2pkDBK19AP2ga+Ph7xrMYP zs7BRF7sTemr9/HeTbspDCMFu+0Iac9yUidouuYQxQiGjuFOMfQ6LZv9tXkqi2FB4NIjNNDb7Y56l OBuNt1reevjAQec42yudI4XutVduTtoXAHiz/p+N/tgM47NLMsoMytepzFHyd3hT2Qz7/3UJ2a/wu Nl2o1LKLBLZZMWUqKrcg==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668594480; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fetjyNVdxegk0QG4w8mo8gn6x0g2HdvFN8vnJqqr3gA=; b=c/GS3sElX0D9F335v3oyyBxgxhPMt29fNdOD/oGymgwO2EQQlPFnAIuIJOJiVgVn81dhl3 XW9Iy/aEEEyNrS+A3PCV+tg2DQor6hBBVusp+Q4XJ7THnwXu26qNOLzXddYugRMoJOWSHT Ah+AcgmTo8402fqEB/ZVc255yymxSKs= In-Reply-To: <20221116102659.70287-1-david@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+glud-user-mode-linux-devel=m.gmane-mx.org@lists.infradead.org To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit <> For now, FAULT_FLAG_UNSHARE only applies to anonymous pages, which implies a COW mapping. Let's hide FAULT_FLAG_UNSHARE early if we're not dealing with a COW mapping, such that we treat it like a read fault as documented and don't have to worry about the flag throughout all fault handlers. While at it, centralize the check for mutual exclusion of FAULT_FLAG_UNSHARE and FAULT_FLAG_WRITE and just drop the check that either flag is set in the WP handler. Signed-off-by: David Hildenbrand --- mm/huge_memory.c | 3 --- mm/hugetlb.c | 5 ----- mm/memory.c | 23 ++++++++++++++++++++--- 3 files changed, 20 insertions(+), 11 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ed12cd3acbfd..68d00196b519 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1267,9 +1267,6 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); VM_BUG_ON_VMA(!vma->anon_vma, vma); - VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE)); - VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE)); - if (is_huge_zero_pmd(orig_pmd)) goto fallback; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 1de986c62976..383b26069b33 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5314,9 +5314,6 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr = address & huge_page_mask(h); struct mmu_notifier_range range; - VM_BUG_ON(unshare && (flags & FOLL_WRITE)); - VM_BUG_ON(!unshare && !(flags & FOLL_WRITE)); - /* * hugetlb does not support FOLL_FORCE-style write faults that keep the * PTE mapped R/O such as maybe_mkwrite() would do. @@ -5326,8 +5323,6 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, /* Let's take out MAP_SHARED mappings first. */ if (vma->vm_flags & VM_MAYSHARE) { - if (unlikely(unshare)) - return 0; set_huge_ptep_writable(vma, haddr, ptep); return 0; } diff --git a/mm/memory.c b/mm/memory.c index 2d453736f87c..e014435a87db 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3344,9 +3344,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; struct folio *folio; - VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE)); - VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE)); - if (likely(!unshare)) { if (userfaultfd_pte_wp(vma, *vmf->pte)) { pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -5161,6 +5158,22 @@ static void lru_gen_exit_fault(void) } #endif /* CONFIG_LRU_GEN */ +static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, + unsigned int *flags) +{ + if (unlikely(*flags & FAULT_FLAG_UNSHARE)) { + if (WARN_ON_ONCE(*flags & FAULT_FLAG_WRITE)) + return VM_FAULT_SIGSEGV; + /* + * FAULT_FLAG_UNSHARE only applies to COW mappings. Let's + * just treat it like an ordinary read-fault otherwise. + */ + if (!is_cow_mapping(vma->vm_flags)) + *flags &= ~FAULT_FLAG_UNSHARE; + } + return 0; +} + /* * By the time we get here, we already hold the mm semaphore * @@ -5177,6 +5190,10 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, count_vm_event(PGFAULT); count_memcg_event_mm(vma->vm_mm, PGFAULT); + ret = sanitize_fault_flags(vma, &flags); + if (ret) + return ret; + if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, flags & FAULT_FLAG_INSTRUCTION, flags & FAULT_FLAG_REMOTE)) -- 2.38.1