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Thu, 08 May 2025 09:57:51 -0700 (PDT) Received: from localhost.localdomain ([121.185.186.233]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22fc7742fedsm1678045ad.91.2025.05.08.09.57.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 May 2025 09:57:50 -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 v6] mm/vmalloc: fix data race in show_numa_info() Date: Fri, 9 May 2025 01:56:20 +0900 Message-ID: <20250508165620.15321-1-aha310510@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 82FB040009 X-Stat-Signature: snnjgphwo7p47p7u5que97ac9ksmzcmk X-Rspam-User: X-HE-Tag: 1746723472-714920 X-HE-Meta: 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 cSEdi+KN 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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: 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 --- v6: Change CONFIG_NUMA to must be check before doing any work related to the counters array. - Link to v5: https://lore.kernel.org/all/20250508160800.12540-1-aha310510@gmail.com/ 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 | 63 +++++++++++++++++++++++++++++----------------------- 1 file changed, 35 insertions(+), 28 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ec..c1ea9713a1c0 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; 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 (IS_ENABLED(CONFIG_NUMA)) + show_numa_info(m, v, counters); + seq_putc(m, '\n'); } spin_unlock(&vn->busy.lock); @@ -5023,19 +5035,14 @@ static int vmalloc_info_show(struct seq_file *m, void *p) * As a final step, dump "unpurged" areas. */ show_purge_info(m); + if (IS_ENABLED(CONFIG_NUMA)) + 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); --