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AJvYcCVK8jKzSOEUphHgyjRMsHBQU1uAXRV/hwDf8vB5NYlDwYRpsM8nQfHdjW0oBmXX+ZDOf/Oc6+CCwqO5ayc=@vger.kernel.org X-Gm-Message-State: AOJu0YzfQ4dT1Dt5xTyY4hNE5JW3LG00/dWak/+IiUc5r3ojMnyq3Ecb D+cj5TMkYQiNNrP88oMuHcehf1H34F8AA0XGwQxkVj1MC20tAk8a+drsk9NPlREw1OxzhafKikH tcg/+NfNISg6r29EiUHOc+MEE+g== X-Google-Smtp-Source: AGHT+IGScETQx55bga4w6kvGfG7E35WD9DziDa+ZAZXqWYfQigIxpcLfBDKsXWxtq04osZKOoTiH4wackQ/kqzmTPQ== X-Received: from pjtf24.prod.google.com ([2002:a17:90a:c298:b0:339:ee20:f620]) (user=kaleshsingh job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1b11:b0:32e:38b0:15f4 with SMTP id 98e67ed59e1d1-33b51149231mr34380315a91.7.1760399746893; Mon, 13 Oct 2025 16:55:46 -0700 (PDT) Date: Mon, 13 Oct 2025 16:51:52 -0700 In-Reply-To: <20251013235259.589015-1-kaleshsingh@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251013235259.589015-1-kaleshsingh@google.com> X-Mailer: git-send-email 2.51.0.760.g7b8bcc2412-goog Message-ID: <20251013235259.589015-2-kaleshsingh@google.com> Subject: [PATCH v3 1/5] mm: fix off-by-one error in VMA count limit checks From: Kalesh Singh To: akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, david@redhat.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de Cc: kernel-team@android.com, android-mm@google.com, Kalesh Singh , stable@vger.kernel.org, SeongJae Park , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jann Horn , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The VMA count limit check in do_mmap() and do_brk_flags() uses a strict inequality (>), which allows a process's VMA count to exceed the configured sysctl_max_map_count limit by one. A process with mm->map_count =3D=3D sysctl_max_map_count will incorrectly pass this check and then exceed the limit upon allocation of a new VMA when its map_count is incremented. Other VMA allocation paths, such as split_vma(), already use the correct, inclusive (>=3D) comparison. Fix this bug by changing the comparison to be inclusive in do_mmap() and do_brk_flags(), bringing them in line with the correct behavior of other allocation paths. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: Cc: Andrew Morton Cc: David Hildenbrand Cc: "Liam R. Howlett" Cc: Lorenzo Stoakes Cc: Mike Rapoport Cc: Minchan Kim Cc: Pedro Falcato Reviewed-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Reviewed-by: Pedro Falcato Acked-by: SeongJae Park Signed-off-by: Kalesh Singh --- Changes in v3: - Collect Reviewed-by and Acked-by tags. Changes in v2: - Fix mmap check, per Pedro mm/mmap.c | 2 +- mm/vma.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 644f02071a41..da2cbdc0f87b 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -374,7 +374,7 @@ unsigned long do_mmap(struct file *file, unsigned long = addr, return -EOVERFLOW; =20 /* Too many mappings? */ - if (mm->map_count > sysctl_max_map_count) + if (mm->map_count >=3D sysctl_max_map_count) return -ENOMEM; =20 /* diff --git a/mm/vma.c b/mm/vma.c index a2e1ae954662..fba68f13e628 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2797,7 +2797,7 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm_= area_struct *vma, if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) return -ENOMEM; =20 - if (mm->map_count > sysctl_max_map_count) + if (mm->map_count >=3D sysctl_max_map_count) return -ENOMEM; =20 if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) --=20 2.51.0.760.g7b8bcc2412-goog