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Thu, 08 May 2025 09:08:24 -0700 (PDT) Received: from localhost.localdomain ([121.185.186.233]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22fc8271ad5sm879805ad.137.2025.05.08.09.08.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 May 2025 09:08:23 -0700 (PDT) From: Jeongjun Park To: akpm@linux-foundation.org Cc: urezki@gmail.com, edumazet@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jeongjun Park Subject: [PATCH v5] mm/vmalloc: fix data race in show_numa_info() Date: Fri, 9 May 2025 01:07:59 +0900 Message-ID: <20250508160800.12540-1-aha310510@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 950A240013 X-Stat-Signature: bgxxie8yedy7e4wiqadwfmasefgwgg8h X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1746720505-559501 X-HE-Meta: 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 AMi5Hs3B rTqJtUQ7eBx9zupDStpvBA+gjQv1IEc7ZzQRc3lZU2yKwDWXNUWCpKCl5TknAAGiUmJmYPOwgywE11iUAFgDup+CQVj369/eGCDJS7VIQHmGJ6OsEr3CdQUZwFO3dxJKytciFUmdtlmcSi3gnRMwwvRV0LYGMpl+4J6xCrGMQOSYnomDK/LBkrx0qLV9A6n+1Jth9jRtPhxmcU9tZh2KQlYiJ+aWlhRPqbqsLxZS8Cc//b3ugKOFS2EzzeccqV/1f+7vHdsFg+BcBIWdc2rOq6j8P8wu0i4eROJhDbmybe8lbh1cPDcNYyMgh/AIol0tmvqvgtPAQUAsXmgRQX7tsQL8GjfE/c/pZWFOYgqlVZoSSZXpkOPvT7V0V5jz4HJuI70Dl3RkoI4Fpd8HjAxAxxWMTspczV9INAZluMh292Pna3hun8YjwU9Kkz26+dKATu4a+dayeSTl0mJELvh+8+p1w/XUgaX0Of8ZsObdvMAhhmBCgDuRGj/PzpWDGRscId8KvIk7Ne8raOH5N8fMqLSrU6w== 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: The following data-race was found in show_numa_info(): ================================================================== BUG: KCSAN: data-race in vmalloc_info_show / vmalloc_info_show read to 0xffff88800971fe30 of 4 bytes by task 8289 on cpu 0: show_numa_info mm/vmalloc.c:4936 [inline] vmalloc_info_show+0x5a8/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 .... write to 0xffff88800971fe30 of 4 bytes by task 8287 on cpu 1: show_numa_info mm/vmalloc.c:4934 [inline] vmalloc_info_show+0x38f/0x7e0 mm/vmalloc.c:5016 seq_read_iter+0x373/0xb40 fs/seq_file.c:230 proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 .... value changed: 0x0000008f -> 0x00000000 ================================================================== According to this report,there is a read/write data-race because m->private is accessible to multiple CPUs. To fix this, instead of allocating the heap in proc_vmalloc_init() and passing the heap address to m->private, vmalloc_info_show() should allocate the heap. Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information") Suggested-by: Eric Dumazet Suggested-by: Uladzislau Rezki (Sony) Suggested-by: Andrew Morton Signed-off-by: Jeongjun Park --- v5: Change heap to be allocated only when CONFIG_NUMA is enabled - Link to v4: https://lore.kernel.org/all/20250508065558.149091-1-aha310510@gmail.com/ v4: Change the way counters array heap is allocated, per Andrew Morton's suggestion. And fix it to call smp_rmb() in the correct location. - Link to v3: https://lore.kernel.org/all/20250507142552.9446-1-aha310510@gmail.com/ v3: Following Uladzislau Rezki's suggestion, we check v->flags beforehand to avoid printing uninitialized members of vm_struct. - Link to v2: https://lore.kernel.org/all/20250506082520.84153-1-aha310510@gmail.com/ v2: Refactoring some functions and fix patch as per Eric Dumazet suggestion - Link to v1: https://lore.kernel.org/all/20250505171948.24410-1-aha310510@gmail.com/ --- mm/vmalloc.c | 62 ++++++++++++++++++++++++++++------------------------ 1 file changed, 34 insertions(+), 28 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ec..866f18766dfc 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3100,7 +3100,7 @@ static void clear_vm_uninitialized_flag(struct vm_struct *vm) /* * Before removing VM_UNINITIALIZED, * we should make sure that vm has proper values. - * Pair with smp_rmb() in show_numa_info(). + * Pair with smp_rmb() in vread_iter() and vmalloc_info_show(). */ smp_wmb(); vm->flags &= ~VM_UNINITIALIZED; @@ -4914,28 +4914,29 @@ bool vmalloc_dump_obj(void *object) #endif #ifdef CONFIG_PROC_FS -static void show_numa_info(struct seq_file *m, struct vm_struct *v) -{ - if (IS_ENABLED(CONFIG_NUMA)) { - unsigned int nr, *counters = m->private; - unsigned int step = 1U << vm_area_page_order(v); - if (!counters) - return; +/* + * Print number of pages allocated on each memory node. + * + * This function can only be called if CONFIG_NUMA is enabled + * and VM_UNINITIALIZED bit in v->flags is disabled. + */ +static void show_numa_info(struct seq_file *m, struct vm_struct *v, + unsigned int *counters) +{ + unsigned int nr; + unsigned int step = 1U << vm_area_page_order(v); - if (v->flags & VM_UNINITIALIZED) - return; - /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ - smp_rmb(); + if (!counters) + return; - memset(counters, 0, nr_node_ids * sizeof(unsigned int)); + memset(counters, 0, nr_node_ids * sizeof(unsigned int)); - for (nr = 0; nr < v->nr_pages; nr += step) - counters[page_to_nid(v->pages[nr])] += step; - for_each_node_state(nr, N_HIGH_MEMORY) - if (counters[nr]) - seq_printf(m, " N%u=%u", nr, counters[nr]); - } + for (nr = 0; nr < v->nr_pages; nr += step) + counters[page_to_nid(v->pages[nr])] += step; + for_each_node_state(nr, N_HIGH_MEMORY) + if (counters[nr]) + seq_printf(m, " N%u=%u", nr, counters[nr]); } static void show_purge_info(struct seq_file *m) @@ -4962,8 +4963,12 @@ static int vmalloc_info_show(struct seq_file *m, void *p) struct vmap_node *vn; struct vmap_area *va; struct vm_struct *v; + unsigned int *counters = NULL; int i; + if (IS_ENABLED(CONFIG_NUMA)) + counters = kmalloc(nr_node_ids * sizeof(unsigned int), GFP_KERNEL); + for (i = 0; i < nr_vmap_nodes; i++) { vn = &vmap_nodes[i]; @@ -4979,6 +4984,11 @@ static int vmalloc_info_show(struct seq_file *m, void *p) } v = va->vm; + if (v->flags & VM_UNINITIALIZED) + continue; + + /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ + smp_rmb(); seq_printf(m, "0x%pK-0x%pK %7ld", v->addr, v->addr + v->size, v->size); @@ -5013,7 +5023,9 @@ static int vmalloc_info_show(struct seq_file *m, void *p) if (is_vmalloc_addr(v->pages)) seq_puts(m, " vpages"); - show_numa_info(m, v); + if (counters) + show_numa_info(m, v, counters); + seq_putc(m, '\n'); } spin_unlock(&vn->busy.lock); @@ -5023,19 +5035,13 @@ static int vmalloc_info_show(struct seq_file *m, void *p) * As a final step, dump "unpurged" areas. */ show_purge_info(m); + kfree(counters); return 0; } static int __init proc_vmalloc_init(void) { - void *priv_data = NULL; - - if (IS_ENABLED(CONFIG_NUMA)) - priv_data = kmalloc(nr_node_ids * sizeof(unsigned int), GFP_KERNEL); - - proc_create_single_data("vmallocinfo", - 0400, NULL, vmalloc_info_show, priv_data); - + proc_create_single("vmallocinfo", 0400, NULL, vmalloc_info_show); return 0; } module_init(proc_vmalloc_init); --