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(p200300cbc70024006b7902aa96027016.dip0.t-ipconnect.de. [2003:cb:c700:2400:6b79:2aa:9602:7016]) by smtp.gmail.com with ESMTPSA id c10-20020adffb0a000000b00306344eaebfsm2359522wrr.28.2023.05.02.04.29.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 May 2023 04:29:16 -0700 (PDT) Message-ID: <06301913-9289-6654-5851-16cf8066c6b4@redhat.com> Date: Tue, 2 May 2023 13:29:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH] mm/mmap/vma_merge: always check invariants To: Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: "Liam R . Howlett" , Vlastimil Babka References: From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 30.04.23 22:19, Lorenzo Stoakes wrote: > We may still have inconsistent input parameters even if we choose not to > merge and the vma_merge() invariant checks are useful for checking this > with no production runtime cost (these are only relevant when > CONFIG_DEBUG_VM is specified). > > Therefore, perform these checks regardless of whether we merge. > > This is relevant, as a recent issue (addressed in commit "mm/mempolicy: > Correctly update prev when policy is equal on mbind") in the mbind logic > was only picked up in the 6.2.y stable branch where these assertions are > performed prior to determining mergeability. > > Had this remained the same in mainline this issue may have been picked up > faster, so moving forward let's always check them. > > Signed-off-by: Lorenzo Stoakes > --- > mm/mmap.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 5522130ae606..13678edaa22c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -960,17 +960,17 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > merge_next = true; > } > > + /* Verify some invariant that must be enforced by the caller. */ > + VM_WARN_ON(prev && addr <= prev->vm_start); > + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > + VM_WARN_ON(addr >= end); > + > if (!merge_prev && !merge_next) > return NULL; /* Not mergeable. */ > > res = vma = prev; > remove = remove2 = adjust = NULL; > > - /* Verify some invariant that must be enforced by the caller. */ > - VM_WARN_ON(prev && addr <= prev->vm_start); > - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > - VM_WARN_ON(addr >= end); > - > /* Can we merge both the predecessor and the successor? */ > if (merge_prev && merge_next && > is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) { Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb