linux-kernel - Re: [PATCH v3] mm: shrinker: avoid memleak in alloc_shrinker

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Message-ID: <nfxjrdg36rykyjeit7o7jdxaf7h2ta2wbixktf3g6a25vr3qyi@yfcjctjt67g3>
Date: Fri, 25 Oct 2024 12:12:34 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: akpm@...ux-foundation.org, david@...morbit.com, 
	zhengqi.arch@...edance.com, roman.gushchin@...ux.dev, muchun.song@...ux.dev, 
	anshuman.khandual@....com, vbabka@...e.cz, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	chenridong@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH v3] mm: shrinker: avoid memleak in alloc_shrinker_info

On Fri, Oct 25, 2024 at 06:09:42AM +0000, Chen Ridong 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

This dump doesn't add much value to the commit message.

> 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>
> Acked-by: Qi Zheng <zhengqi.arch@...edance.com>
> Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov