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AJvYcCX8KULZBy6Ql8sNE6qnbr8Xv/mQlNIz7/ZvMCvnX5Ud70ib/I5crP0dEC77rUoflQ/GsCCSDuZbm14FilE=@vger.kernel.org X-Gm-Message-State: AOJu0Yxs01zpNgW+7J2BreAbbIJBSmNUYcKBYHSNo+4J0D4T5RlouSNt xbQ4t7vYMl+aTSVbEs8dLq7Q+ZvoGY2Jo2TsklcBIEnqoNc6VxJX7WYrSTDAU+YO/wo+frtGJtc f8v3MBbaU+zQErPOdjeVuctoLIg== X-Google-Smtp-Source: AGHT+IETeFsnzxOgNLMCiDHUaYpnu2vRB/Fb66R7+b7xgDA1s+PPQqB4+bTMKY9LvQ479LuxEWFmKDI75ZPJsp8Xlg== X-Received: from plkb5.prod.google.com ([2002:a17:903:fa5:b0:264:7b3c:4fe4]) (user=kaleshsingh job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:dac2:b0:24b:1585:6350 with SMTP id d9443c01a7336-25d2ac3c545mr185756655ad.11.1757954752355; Mon, 15 Sep 2025 09:45:52 -0700 (PDT) Date: Mon, 15 Sep 2025 09:36:32 -0700 In-Reply-To: <20250915163838.631445-1-kaleshsingh@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250915163838.631445-1-kaleshsingh@google.com> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250915163838.631445-2-kaleshsingh@google.com> Subject: [PATCH v2 1/7] 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, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Jann Horn , 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 Signed-off-by: Kalesh Singh Acked-by: SeongJae Park Reviewed-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Reviewed-by: Pedro Falcato --- Chnages 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 7306253cc3b5..e5370e7fcd8f 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 3b12c7579831..033a388bc4b1 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -2772,7 +2772,7 @@ 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 2.51.0.384.g4c02a37b29-goog