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Sat, 08 Jul 2023 12:12:18 -0700 (PDT) Date: Sat, 8 Jul 2023 12:12:11 -0700 In-Reply-To: <20230708191212.4147700-1-surenb@google.com> Mime-Version: 1.0 References: <20230708191212.4147700-1-surenb@google.com> X-Mailer: git-send-email 2.41.0.390.g38632f3daf-goog Message-ID: <20230708191212.4147700-2-surenb@google.com> Subject: [PATCH v2 2/3] mm: lock newly mapped VMA which can be modified after it becomes visible From: Suren Baghdasaryan To: torvalds@linux-foundation.org Cc: akpm@linux-foundation.org, regressions@leemhuis.info, bagasdotme@gmail.com, jacobly.alt@gmail.com, willy@infradead.org, liam.howlett@oracle.com, david@redhat.com, peterx@redhat.com, ldufour@linux.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, gregkh@linuxfoundation.org, regressions@lists.linux.dev, Suren Baghdasaryan , stable@vger.kernel.org X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B75CAC000F X-Stat-Signature: p4b8w385pp34jfpkrt9oymxa89hpk1ap X-Rspam-User: X-HE-Tag: 1688843539-394212 X-HE-Meta: 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 LuXmjbbs 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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: mmap_region adds a newly created VMA into VMA tree and might modify it afterwards before dropping the mmap_lock. This poses a problem for page faults handled under per-VMA locks because they don't take the mmap_lock and can stumble on this VMA while it's still being modified. Currently this does not pose a problem since post-addition modifications are done only for file-backed VMAs, which are not handled under per-VMA lock. However, once support for handling file-backed page faults with per-VMA locks is added, this will become a race. Fix this by write-locking the VMA before inserting it into the VMA tree. Other places where a new VMA is added into VMA tree do not modify it after the insertion, so do not need the same locking. Cc: stable@vger.kernel.org Signed-off-by: Suren Baghdasaryan --- mm/mmap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index c66e4622a557..84c71431a527 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2812,6 +2812,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, if (vma->vm_file) i_mmap_lock_write(vma->vm_file->f_mapping); + /* Lock the VMA since it is modified after insertion into VMA tree */ + vma_start_write(vma); vma_iter_store(&vmi, vma); mm->map_count++; if (vma->vm_file) {