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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: 8e1d743f2c ("mm: vmalloc: support multiple nodes in vmallocinfo")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pull/1253/head
Jeongjun Park 2025-05-09 01:56:20 +09:00 committed by Andrew Morton
parent b65e4b56e9
commit 5c5f0468d1
1 changed files with 35 additions and 28 deletions
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63
mm/vmalloc.c
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@ -3109,7 +3109,7 @@ static void clear_vm_uninitialized_flag(struct vm_struct *vm)
/* /*
* Before removing VM_UNINITIALIZED, * Before removing VM_UNINITIALIZED,
* we should make sure that vm has proper values. * 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(); smp_wmb();
vm->flags &= ~VM_UNINITIALIZED; vm->flags &= ~VM_UNINITIALIZED;
@ -4939,28 +4939,29 @@ bool vmalloc_dump_obj(void *object)
#endif #endif
#ifdef CONFIG_PROC_FS #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;
unsigned int nr, *counters = m->private; unsigned int step = 1U << vm_area_page_order(v);
unsigned int step = 1U << vm_area_page_order(v);
if (!counters) if (!counters)
return; return;
if (v->flags & VM_UNINITIALIZED) memset(counters, 0, nr_node_ids * sizeof(unsigned int));
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)
counters[page_to_nid(v->pages[nr])] += step;
for (nr = 0; nr < v->nr_pages; nr += step) for_each_node_state(nr, N_HIGH_MEMORY)
counters[page_to_nid(v->pages[nr])] += step; if (counters[nr])
for_each_node_state(nr, N_HIGH_MEMORY) seq_printf(m, " N%u=%u", nr, counters[nr]);
if (counters[nr])
seq_printf(m, " N%u=%u", nr, counters[nr]);
}
} }
static void show_purge_info(struct seq_file *m) 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_node *vn;
struct vmap_area *va; struct vmap_area *va;
struct vm_struct *v; 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) { for_each_vmap_node(vn) {
spin_lock(&vn->busy.lock); spin_lock(&vn->busy.lock);
@ -4998,6 +5003,11 @@ static int vmalloc_info_show(struct seq_file *m, void *p)
} }
v = va->vm; 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", seq_printf(m, "0x%pK-0x%pK %7ld",
v->addr, v->addr + v->size, v->size); 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)) if (is_vmalloc_addr(v->pages))
seq_puts(m, " vpages"); seq_puts(m, " vpages");
show_numa_info(m, v); if (IS_ENABLED(CONFIG_NUMA))
show_numa_info(m, v, counters);
seq_putc(m, '\n'); seq_putc(m, '\n');
} }
spin_unlock(&vn->busy.lock); 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. * As a final step, dump "unpurged" areas.
*/ */
show_purge_info(m); show_purge_info(m);
if (IS_ENABLED(CONFIG_NUMA))
kfree(counters);
return 0; return 0;
} }
static int __init proc_vmalloc_init(void) static int __init proc_vmalloc_init(void)
{ {
void *priv_data = NULL; proc_create_single("vmallocinfo", 0400, NULL, vmalloc_info_show);
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);
return 0; return 0;
} }
module_init(proc_vmalloc_init); module_init(proc_vmalloc_init);