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bh=GQTFxYC9vfA9jf0qnv7gyPX3j3jACtIk3rCkUF/FJDY=; b=gSSA39FuZ9YYOzaCXOwot6McLcK/dVo4hRn8L5m2ChUPc1EhjsAyUFxxGdlgWEUzgX 0sj5u/MLOTsBsr0ba1MPphYTWo1iyJhWPVVxOJnvPP4PsKNDDbi4fkkUt/UjgPDFfSBl cN6a7k/Ind58YBpwKbEVDFog9HjiZLD6jmYAEKr8kCI93Y5wvbFiZTus9XCY6zIjjlrF iAv1L9lpYV+An1lSR7dejsMWEwBr0D0nlagBlQXj6PL4fgQCEF+XvDOXIBgzSLNcB28c /88ibp/GNbEU02P/zISYkE7T23bstNfyznOTAxzwWCn0zJOo3Qm+usV0lD9/fXxiU4xM GEmA== X-Gm-Message-State: AO0yUKWiXfz6EPUIxmYrvAPojVbc1png1U0hxDoSeA1PSz8oV3/w0TDj rMM22zOSaCBBbe3tDMEj6FesxROyXJY= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:e1f6:21d1:eead:3897]) (user=surenb job=sendgmr) by 2002:a0d:ca10:0:b0:52e:e6ed:3094 with SMTP id m16-20020a0dca10000000b0052ee6ed3094mr727498ywd.532.1677519461069; Mon, 27 Feb 2023 09:37:41 -0800 (PST) Date: Mon, 27 Feb 2023 09:36:26 -0800 In-Reply-To: <20230227173632.3292573-1-surenb@google.com> Mime-Version: 1.0 References: <20230227173632.3292573-1-surenb@google.com> X-Mailer: git-send-email 2.39.2.722.g9855ee24e9-goog Message-ID: <20230227173632.3292573-28-surenb@google.com> Subject: [PATCH v4 27/33] mm: prevent userfaults to be handled under per-vma lock From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, chriscli@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, leewalsh@google.com, posk@google.com, michalechner92@googlemail.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com, Suren Baghdasaryan X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759006872894351620?= X-GMAIL-MSGID: =?utf-8?q?1759006872894351620?= Due to the possibility of handle_userfault dropping mmap_lock, avoid fault handling under VMA lock and retry holding mmap_lock. This can be handled more gracefully in the future. Signed-off-by: Suren Baghdasaryan Suggested-by: Peter Xu --- mm/memory.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index af3c2c59cd11..f734f80d28ca 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5255,6 +5255,15 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, if (!vma_start_read(vma)) goto inval; + /* + * Due to the possibility of userfault handler dropping mmap_lock, avoid + * it for now and fall back to page fault handling under mmap_lock. + */ + if (userfaultfd_armed(vma)) { + vma_end_read(vma); + goto inval; + } + /* Check since vm_start/vm_end might change before we lock the VMA */ if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { vma_end_read(vma);