[PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Jeongjun Park]

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 <edumazet@google.com>
Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
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);
--

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Uladzislau Rezki]

On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> 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 <edumazet@google.com>
> Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---
> 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);
> --
LGTM:

Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>

Thank you!

--
Uladzislau Rezki

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Uladzislau Rezki]

On Thu, May 08, 2025 at 07:48:55PM +0200, Uladzislau Rezki wrote:
> On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> > 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 <edumazet@google.com>
> > Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > ---
> > 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);
> > --
> LGTM:
> 
> Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
> 
> Thank you!
>
Also one thing i have just noticed. The "Fixes tag" should be updated to
this: Fixes: 8e1d743f2c26 ("mm: vmalloc: support multiple nodes in vmallocinfo")

the below one should not be blamed:

Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information")

Thanks!

--
Uladzislau Rezki

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Jeongjun Park]

Uladzislau Rezki <urezki@gmail.com> wrote:
>
> On Thu, May 08, 2025 at 07:48:55PM +0200, Uladzislau Rezki wrote:
> > On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> > > 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 <edumazet@google.com>
> > > Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> > > Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > > ---
> > > 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);
> > > --
> > LGTM:
> >
> > Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
> >
> > Thank you!
> >
> Also one thing i have just noticed. The "Fixes tag" should be updated to
> this: Fixes: 8e1d743f2c26 ("mm: vmalloc: support multiple nodes in vmallocinfo")
>
> the below one should not be blamed:
>
> Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information")
>
> Thanks!
>
> --
> Uladzislau Rezki

I've been looking through the stable tree and it seems like this issue
still exists in the stable tree, so I think this patch needs to be
backported.

What do you think?

Regards,
Jeongjun Park

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Uladzislau Rezki]

On Wed, Jul 02, 2025 at 01:01:13AM +0900, Jeongjun Park wrote:
> Uladzislau Rezki <urezki@gmail.com> wrote:
> >
> > On Thu, May 08, 2025 at 07:48:55PM +0200, Uladzislau Rezki wrote:
> > > On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> > > > 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 <edumazet@google.com>
> > > > Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > > Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> > > > Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > > > ---
> > > > 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);
> > > > --
> > > LGTM:
> > >
> > > Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
> > >
> > > Thank you!
> > >
> > Also one thing i have just noticed. The "Fixes tag" should be updated to
> > this: Fixes: 8e1d743f2c26 ("mm: vmalloc: support multiple nodes in vmallocinfo")
> >
> > the below one should not be blamed:
> >
> > Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information")
> >
> > Thanks!
> >
> > --
> > Uladzislau Rezki
> 
> I've been looking through the stable tree and it seems like this issue
> still exists in the stable tree, so I think this patch needs to be
> backported.
> 
> What do you think?
> 
If the stable does not have it, we should backport it. But it has to be
done only for those where a vmap-node logic is in place. It was delivered
starting from the v6.9 kernel version.

--
Uladzislau Rezki

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Jeongjun Park]

Uladzislau Rezki <urezki@gmail.com> wrote:
>
> On Wed, Jul 02, 2025 at 01:01:13AM +0900, Jeongjun Park wrote:
> > Uladzislau Rezki <urezki@gmail.com> wrote:
> > >
> > > On Thu, May 08, 2025 at 07:48:55PM +0200, Uladzislau Rezki wrote:
> > > > On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> > > > > 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 <edumazet@google.com>
> > > > > Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > > > Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> > > > > Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > > > > ---
> > > > > 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);
> > > > > --
> > > > LGTM:
> > > >
> > > > Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
> > > >
> > > > Thank you!
> > > >
> > > Also one thing i have just noticed. The "Fixes tag" should be updated to
> > > this: Fixes: 8e1d743f2c26 ("mm: vmalloc: support multiple nodes in vmallocinfo")
> > >
> > > the below one should not be blamed:
> > >
> > > Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information")
> > >
> > > Thanks!
> > >
> > > --
> > > Uladzislau Rezki
> >
> > I've been looking through the stable tree and it seems like this issue
> > still exists in the stable tree, so I think this patch needs to be
> > backported.
> >
> > What do you think?
> >
> If the stable does not have it, we should backport it. But it has to be
> done only for those where a vmap-node logic is in place. It was delivered
> starting from the v6.9 kernel version.
>

Then I guess I should backport to 6.12, 6.15. Thanks for letting me know!

Regards,
Jeongjun Park

Re: [PATCH v6] mm/vmalloc: fix data race in show_numa_info()

[Uladzislau Rezki]

On Wed, Jul 02, 2025 at 11:01:23PM +0900, Jeongjun Park wrote:
> Uladzislau Rezki <urezki@gmail.com> wrote:
> >
> > On Wed, Jul 02, 2025 at 01:01:13AM +0900, Jeongjun Park wrote:
> > > Uladzislau Rezki <urezki@gmail.com> wrote:
> > > >
> > > > On Thu, May 08, 2025 at 07:48:55PM +0200, Uladzislau Rezki wrote:
> > > > > On Fri, May 09, 2025 at 01:56:20AM +0900, Jeongjun Park wrote:
> > > > > > 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 <edumazet@google.com>
> > > > > > Suggested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > > > > Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> > > > > > Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> > > > > > ---
> > > > > > 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);
> > > > > > --
> > > > > LGTM:
> > > > >
> > > > > Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
> > > > >
> > > > > Thank you!
> > > > >
> > > > Also one thing i have just noticed. The "Fixes tag" should be updated to
> > > > this: Fixes: 8e1d743f2c26 ("mm: vmalloc: support multiple nodes in vmallocinfo")
> > > >
> > > > the below one should not be blamed:
> > > >
> > > > Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information")
> > > >
> > > > Thanks!
> > > >
> > > > --
> > > > Uladzislau Rezki
> > >
> > > I've been looking through the stable tree and it seems like this issue
> > > still exists in the stable tree, so I think this patch needs to be
> > > backported.
> > >
> > > What do you think?
> > >
> > If the stable does not have it, we should backport it. But it has to be
> > done only for those where a vmap-node logic is in place. It was delivered
> > starting from the v6.9 kernel version.
> >
> 
> Then I guess I should backport to 6.12, 6.15. Thanks for letting me know!
> 
You are welcome!

--
Uladzislau Rezki