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bh=dtbb/rgJDVPG5hb8ydKzjEL35WMZYcFrpyL4j03oF8s=; b=qOUIpBPL+rpft3hZySD7KKTVnepWMqlG6hLPEcKmV4cggdRv1DCq+7V1plUbCs951X lxMH/szkt80Br8JxeG/hL0bKBtnz+4Box8316nGao3F1fjd8lEUK6ofTduGEO1YctdHS ejvqbRHp/TIV1v5Q+Y2zmBbFzAG4QwyhrGqUObzpVIDH8EeMjkhYzAA6rZGeS/yA+JBc ggcv7ztumPD6pY+APTxeGzXS2QpTmAJjOqmhtZuLAZnWLN7He9ZsbLfSZO0lfcYZeC1a NKMWQh7o2pLJ9oL98hwmBqsiH5GimfUl5sNpxN1iOqz//I99LkjJt4JRNxQV2DecaMl4 oMSw== X-Gm-Message-State: AFqh2kqfZfJYOvJouHXBZLzvGYCzq190xmj8L7HZdkMWzzivaLCejg0S KEZOYTGRFj2I+TAVWWInPflYWhwxsJM= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:4e19:be9:c5d0:8483]) (user=surenb job=sendgmr) by 2002:a0d:fc86:0:b0:4db:3ac0:78a3 with SMTP id m128-20020a0dfc86000000b004db3ac078a3mr5702708ywf.266.1674848538548; Fri, 27 Jan 2023 11:42:18 -0800 (PST) Date: Fri, 27 Jan 2023 11:41:04 -0800 In-Reply-To: <20230127194110.533103-1-surenb@google.com> Mime-Version: 1.0 References: <20230127194110.533103-1-surenb@google.com> X-Mailer: git-send-email 2.39.1.456.gfc5497dd1b-goog Message-ID: <20230127194110.533103-28-surenb@google.com> Subject: [PATCH v2 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, 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, 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, surenb@google.com 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?1756206274317195919?= X-GMAIL-MSGID: =?utf-8?q?1756206274317195919?= 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 33ecc850d3cb..55582c6fa2fd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5256,6 +5256,15 @@ 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);