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Message-Id: <ABC60698-90FC-4F91-A25E-AF30640B38A9@linux.dev>
Date: Mon, 14 Oct 2024 14:25:04 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: akpm@...ux-foundation.org,
david@...morbit.com,
zhengqi.arch@...edance.com,
roman.gushchin@...ux.dev,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
chenridong@...wei.com,
wangweiyang2@...wei.com
Subject: Re: [PATCH v2] mm: shrinker: avoid memleak in alloc_shrinker_info
> On Oct 14, 2024, at 11:23, Chen Ridong <chenridong@...weicloud.com> wrote:
>
> 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 | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/shrinker.c b/mm/shrinker.c
> index dc5d2a6fcfc4..92270413190d 100644
> --- a/mm/shrinker.c
> +++ b/mm/shrinker.c
> @@ -97,6 +97,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
>
> err:
> mutex_unlock(&shrinker_mutex);
> + kvfree(info);
Please transpose kvfree() to the place above mutex_unlock().
We should release the resources in the order which is inverse
to the that of acquiring resources.
Thanks.
> free_shrinker_info(memcg);
> return -ENOMEM;
> }
> --
> 2.34.1
>
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