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AJvYcCVIdmzjyeXZEQs2NopRchAVSucefUN8foWvIISOC3DcXAk0C6PmZAkjHMSavqBdA3W0qzJYw6WBwA==@kvack.org X-Gm-Message-State: AOJu0YyNdE6idv1xVtO/Yiuh+7OIuVerK3TqCUoWPE0JiTqt3XUaesm/ yX9PwUHRf6iFsppQMl77J9ddravGQuHO27cKNLsaA4RfUxolYOsGbNwu5IIpjLUQl/KxoATn627 PCw== X-Google-Smtp-Source: AGHT+IGMj8N9UltRndmqK4fcmCOY71dV/ZTT0TWqfMv3mL8UIMVUEmmB9CXosWINwjoG+HVa2iESOUWrDew= X-Received: from pfblc21.prod.google.com ([2002:a05:6a00:4f55:b0:730:9378:98c1]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:2585:b0:1ea:e81c:60fa with SMTP id adf61e73a8af0-1ee5c78b20bmr13938165637.20.1739486852080; Thu, 13 Feb 2025 14:47:32 -0800 (PST) Date: Thu, 13 Feb 2025 14:46:53 -0800 In-Reply-To: <20250213224655.1680278-1-surenb@google.com> Mime-Version: 1.0 References: <20250213224655.1680278-1-surenb@google.com> X-Mailer: git-send-email 2.48.1.601.g30ceb7b040-goog Message-ID: <20250213224655.1680278-17-surenb@google.com> Subject: [PATCH v10 16/18] mm: prepare lock_vma_under_rcu() for vma reuse possibility From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, richard.weiyang@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com X-Rspam-User: X-Rspamd-Queue-Id: 2D1D0180005 X-Rspamd-Server: rspam07 X-Stat-Signature: id89q9as4nawkxbjbopmuhdraojrjy14 X-HE-Tag: 1739486852-788487 X-HE-Meta: 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 KcBetd0i 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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: Once we make vma cache SLAB_TYPESAFE_BY_RCU, it will be possible for a vma to be reused and attached to another mm after lock_vma_under_rcu() locks the vma. lock_vma_under_rcu() should ensure that vma_start_read() is using the original mm and after locking the vma it should ensure that vma->vm_mm has not changed from under us. Signed-off-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka --- include/linux/mm.h | 12 ++++++++---- mm/memory.c | 7 ++++--- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 327cf5944569..88693568c9ef 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -739,10 +739,13 @@ static inline void vma_refcount_put(struct vm_area_struct *vma) * Try to read-lock a vma. The function is allowed to occasionally yield false * locked result to avoid performance overhead, in which case we fall back to * using mmap_lock. The function should never yield false unlocked result. + * False locked result is possible if mm_lock_seq overflows or if vma gets + * reused and attached to a different mm before we lock it. * Returns the vma on success, NULL on failure to lock and EAGAIN if vma got * detached. */ -static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma) +static inline struct vm_area_struct *vma_start_read(struct mm_struct *mm, + struct vm_area_struct *vma) { int oldcnt; @@ -753,7 +756,7 @@ static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma) * we don't rely on for anything - the mm_lock_seq read against which we * need ordering is below. */ - if (READ_ONCE(vma->vm_lock_seq) == READ_ONCE(vma->vm_mm->mm_lock_seq.sequence)) + if (READ_ONCE(vma->vm_lock_seq) == READ_ONCE(mm->mm_lock_seq.sequence)) return NULL; /* @@ -780,7 +783,7 @@ static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma) * after it has been unlocked. * This pairs with RELEASE semantics in vma_end_write_all(). */ - if (unlikely(vma->vm_lock_seq == raw_read_seqcount(&vma->vm_mm->mm_lock_seq))) { + if (unlikely(vma->vm_lock_seq == raw_read_seqcount(&mm->mm_lock_seq))) { vma_refcount_put(vma); return NULL; } @@ -914,7 +917,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, #else /* CONFIG_PER_VMA_LOCK */ static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt) {} -static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma) +static inline struct vm_area_struct *vma_start_read(struct mm_struct *mm, + struct vm_area_struct *vma) { return NULL; } static inline void vma_end_read(struct vm_area_struct *vma) {} static inline void vma_start_write(struct vm_area_struct *vma) {} diff --git a/mm/memory.c b/mm/memory.c index 528407c0d7cf..6378a873e7c1 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6492,7 +6492,7 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, if (!vma) goto inval; - vma = vma_start_read(vma); + vma = vma_start_read(mm, vma); if (IS_ERR_OR_NULL(vma)) { /* Check if the VMA got isolated after we found it */ if (PTR_ERR(vma) == -EAGAIN) { @@ -6512,8 +6512,9 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, * fields are accessible for RCU readers. */ - /* Check since vm_start/vm_end might change before we lock the VMA */ - if (unlikely(address < vma->vm_start || address >= vma->vm_end)) + /* Check if the vma we locked is the right one. */ + if (unlikely(vma->vm_mm != mm || + address < vma->vm_start || address >= vma->vm_end)) goto inval_end_read; rcu_read_unlock();