linux-kernel - [PATCH] mm: shrinker: avoid memleak in alloc_shrinker

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Message-Id: <20241011142105.391157-1-chenridong@huaweicloud.com>
Date: Fri, 11 Oct 2024 14:21:05 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: akpm@...ux-foundation.org,
	david@...morbit.com,
	zhengqi.arch@...edance.com,
	roman.gushchin@...ux.dev,
	muchun.song@...ux.dev
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	chenridong@...wei.com,
	wangweiyang2@...wei.com
Subject: [PATCH] mm: shrinker: avoid memleak in alloc_shrinker_info

From: Chen Ridong <chenridong@...wei.com>

A memleak was found as bellow:

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

In the alloc_shrinker_info function, when shrinker_unit_alloc return
err, the info won't be freed. Just fix it.

Fixes: 307bececcd12 ("mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred}")
Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 mm/shrinker.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/shrinker.c b/mm/shrinker.c
index dc5d2a6fcfc4..e4b795ee6d2e 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -87,8 +87,10 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
 		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);
-- 
2.34.1