linux-kernel - Re: [PATCH] hfs: fix a memleak in hfs_find

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Date: Mon, 29 Jan 2024 17:25:26 +0300
From: Viacheslav Dubeyko <slava@...eyko.com>
To: Zhipeng Lu <alexious@....edu.cn>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
 linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hfs: fix a memleak in hfs_find_init



> On 29 Jan 2024, at 15:54, alexious@....edu.cn wrote:
> 
>>> On 22 Jan 2024, at 20:27, Zhipeng Lu <alexious@....edu.cn> wrote:
>>> 
>>> When the switch statment goes to default and return an error, ptr should
>>> be freed since it is allocated in hfs_find_init.
>>> 
>> 
>> Do you have any memory leaks report? Could you share it in the comments?
>> Which use-case reproduces the issue? It will be easier to review the fix
>> If you can share the path of reproduction.
>> 
>> Thanks,
>> Slava.
> 
> Well, we found this potential memory leak by static analysis.
> 
> We found that all of hfs_find_init's callers won't release `ptr` when 
> hfs_find_init fails, while they will do release `ptr` when functions 
> that after hfs_find_init fails. This tactic observation suggests that
> hfs_find_init proberly should release `ptr` when it fails, i.e. in the
> default branch of switch in this patch.
> 
> Besides, we noticed another implementation of hfs_find_init in 
> fs/hfsplus/bfind.c, which is essentially identical to the one in 
> this patch (in fs/hfs/bfind.c) but calling `BUG();` in default branch
> to trigger an error-handling.
> 

I see. I believe it makes sense to add all of this explanation
into comment section. Modification looks good. Mostly, hfs_find_exit()
does freeing resources and if hfs_find_init() fails, then hfs_find_exit()
is never called. Maybe, it makes sense to set fd->tree = NULL too but
it is not critical, as far as I can see.

Could you please rework the comment section of the patch?

Thanks,
Slava.