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Wed, 07 May 2025 23:56:19 -0700 (PDT) Received: from localhost.localdomain ([118.46.108.16]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22e151e950csm105470145ad.77.2025.05.07.23.56.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 May 2025 23:56:19 -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 v4] mm/vmalloc: fix data race in show_numa_info() Date: Thu, 8 May 2025 15:55:58 +0900 Message-ID: <20250508065558.149091-1-aha310510@gmail.com> X-Mailer: git-send-email 2.47.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: EFC1620009 X-Stat-Signature: ce8a4muxr357azop1b58m8gzf4axfmed X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1746687380-301038 X-HE-Meta: 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 52DbFvg9 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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 --- 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 | 61 ++++++++++++++++++++++++++++------------------------ 1 file changed, 33 insertions(+), 28 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ec..112df5a86106 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 +4963,11 @@ 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; + counters = kmalloc(nr_node_ids * sizeof(unsigned int), GFP_KERNEL); + for (i = 0; i < nr_vmap_nodes; i++) { vn = &vmap_nodes[i]; @@ -4979,6 +4983,11 @@ 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 +5022,9 @@ 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 +5034,13 @@ 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); --