mm: shrinker: avoid memleak in alloc_shrinker_info

A memleak was found as below:

unreferenced object 0xffff8881010d2a80 (size 32):
  comm "mkdir", pid 1559, jiffies 4294932666
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  @...............
  backtrace (crc 2e7ef6fa):
    [<ffffffff81372754>] __kmalloc_node_noprof+0x394/0x470
    [<ffffffff813024ab>] alloc_shrinker_info+0x7b/0x1a0
    [<ffffffff813b526a>] mem_cgroup_css_online+0x11a/0x3b0
    [<ffffffff81198dd9>] online_css+0x29/0xa0
    [<ffffffff811a243d>] cgroup_apply_control_enable+0x20d/0x360
    [<ffffffff811a5728>] cgroup_mkdir+0x168/0x5f0
    [<ffffffff8148543e>] kernfs_iop_mkdir+0x5e/0x90
    [<ffffffff813dbb24>] vfs_mkdir+0x144/0x220
    [<ffffffff813e1c97>] do_mkdirat+0x87/0x130
    [<ffffffff813e1de9>] __x64_sys_mkdir+0x49/0x70
    [<ffffffff81f8c928>] do_syscall_64+0x68/0x140
    [<ffffffff8200012f>] entry_SYSCALL_64_after_hwframe+0x76/0x7e

alloc_shrinker_info(), when shrinker_unit_alloc() returns an errer, the
info won't be freed.  Just fix it.

Link: https://lkml.kernel.org/r/20241025060942.1049263-1-chenridong@huaweicloud.com
Fixes: 307bece ("mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred}")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Wang Weiyang <wangweiyang2@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Chen Ridong

mm/shrinker.c

@@ -76,19 +76,21 @@ void free_shrinker_info(struct mem_cgroup *memcg)
 
 int alloc_shrinker_info(struct mem_cgroup *memcg)
 {
-	struct shrinker_info *info;
 	int nid, ret = 0;
 	int array_size = 0;
 
 	mutex_lock(&shrinker_mutex);
 	array_size = shrinker_unit_size(shrinker_nr_max);
 	for_each_node(nid) {
-		info = kvzalloc_node(sizeof(*info) + array_size, GFP_KERNEL, nid);
+		struct shrinker_info *info = kvzalloc_node(sizeof(*info) + array_size,
+							   GFP_KERNEL, nid);
 		if (!info)
 			goto err;
 		info->map_nr_max = shrinker_nr_max;
-		if (shrinker_unit_alloc(info, NULL, nid))
+		if (shrinker_unit_alloc(info, NULL, nid)) {
+			kvfree(info);
 			goto err;
+		}
 		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
 	}
 	mutex_unlock(&shrinker_mutex);