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[2003:d8:2f27:6d00:7b96:afc9:83d0:5bd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4613d33633bsm32518195e9.11.2025.09.17.03.52.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 03:52:56 -0700 (PDT) Message-ID: Date: Wed, 17 Sep 2025 12:52:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/7] mm: fix off-by-one error in VMA count limit checks To: Kalesh Singh , akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de Cc: kernel-team@android.com, android-mm@google.com, 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 References: <20250915163838.631445-1-kaleshsingh@google.com> <20250915163838.631445-2-kaleshsingh@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BE690C0002 X-Stat-Signature: fixknj5wdxq5anq83cpgrfmc9xxjrem9 X-Rspam-User: X-HE-Tag: 1758106382-402052 X-HE-Meta: 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 G9si18QQ 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 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: List-Subscribe: List-Unsubscribe: On 15.09.25 18:36, Kalesh Singh wrote: > 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 == 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 (>=) 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 > --- Reviewed-by: David Hildenbrand -- Cheers David / dhildenb