Commit 5c5f0468 authored by Jeongjun Park's avatar Jeongjun Park Committed by Andrew Morton
Browse files

mm/vmalloc: fix data race in show_numa_info() 

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.

Link: https://lkml.kernel.org/r/20250508165620.15321-1-aha310510@gmail.com


Fixes: 8e1d743f ("mm: vmalloc: support multiple nodes in vmallocinfo")
Signed-off-by: default avatarJeongjun Park <aha310510@gmail.com>
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatar"Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b65e4b56

mm/vmalloc.c

+35 −28
Original line number Diff line number Diff line
@@ -3109,7 +3109,7 @@ 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;
@@ -4939,20 +4939,22 @@ bool vmalloc_dump_obj(void *object) 
#endif



#ifdef CONFIG_PROC_FS

static void show_numa_info(struct seq_file *m, struct vm_struct *v)



/*

 * 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)

{

	if (IS_ENABLED(CONFIG_NUMA)) {

		unsigned int nr, *counters = m->private;

	unsigned int nr;

	unsigned int step = 1U << vm_area_page_order(v);



	if (!counters)

		return;



		if (v->flags & VM_UNINITIALIZED)

			return;

		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */

		smp_rmb();



	memset(counters, 0, nr_node_ids * sizeof(unsigned int));



	for (nr = 0; nr < v->nr_pages; nr += step)
@@ -4961,7 +4963,6 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v) 
		if (counters[nr])

			seq_printf(m, " N%u=%u", nr, counters[nr]);

}

}



static void show_purge_info(struct seq_file *m)

{
@@ -4984,6 +4985,10 @@ 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;



	if (IS_ENABLED(CONFIG_NUMA))

		counters = kmalloc(nr_node_ids * sizeof(unsigned int), GFP_KERNEL);



	for_each_vmap_node(vn) {

		spin_lock(&vn->busy.lock);
@@ -4998,6 +5003,11 @@ 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);
@@ -5032,7 +5042,9 @@ 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);
@@ -5042,19 +5054,14 @@ 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);