linux-kernel - Re: [PATCH] riscv: module: use a plain variable for list

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Message-ID: <2a902c69-1115-451d-82b7-dcf7641a7c4b@rivosinc.com>
Date: Wed, 27 Nov 2024 15:18:25 +0100
From: Clément Léger <cleger@...osinc.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Charlie Jenkins <charlie@...osinc.com>, zhangkai@...as.ac.cn
Subject: Re: [PATCH] riscv: module: use a plain variable for list_head instead
 of a pointer



On 27/11/2024 15:02, Andrew Jones wrote:
> On Wed, Nov 27, 2024 at 11:30:14AM +0100, Clément Léger wrote:
>> list_head does not need to be allocated, it can be a plain variable.
> 
> rel_head's list_head member, rel_entry, doesn't need to be allocated,
> its storage can just be part of the allocated rel_head.
> 
>> Remove the pointer which allows to get rid of the allocation as well as
>> an existing memory leak.
> 
> It'd be nice to add how the memory leak was found. Inspection or some
> tool?

Yeah sure, it was actually found by Kai Zang, I have added him as Cc but
I can surely give him credit for finding the memleak, I'll add him with
a Reported-by.

Thanks,

Clément

> 
>>
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>>
>> ---
>>  arch/riscv/kernel/module.c | 18 ++++--------------
>>  1 file changed, 4 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
>> index 1cd461f3d872..47d0ebeec93c 100644
>> --- a/arch/riscv/kernel/module.c
>> +++ b/arch/riscv/kernel/module.c
>> @@ -23,7 +23,7 @@ struct used_bucket {
>>  
>>  struct relocation_head {
>>  	struct hlist_node node;
>> -	struct list_head *rel_entry;
>> +	struct list_head rel_entry;
>>  	void *location;
>>  };
>>  
>> @@ -634,7 +634,7 @@ process_accumulated_relocations(struct module *me,
>>  			location = rel_head_iter->location;
>>  			list_for_each_entry_safe(rel_entry_iter,
>>  						 rel_entry_iter_tmp,
>> -						 rel_head_iter->rel_entry,
>> +						 &rel_head_iter->rel_entry,
>>  						 head) {
>>  				curr_type = rel_entry_iter->type;
>>  				reloc_handlers[curr_type].reloc_handler(
>> @@ -704,16 +704,7 @@ static int add_relocation_to_accumulate(struct module *me, int type,
>>  			return -ENOMEM;
>>  		}
>>  
>> -		rel_head->rel_entry =
>> -			kmalloc(sizeof(struct list_head), GFP_KERNEL);
>> -
>> -		if (!rel_head->rel_entry) {
>> -			kfree(entry);
>> -			kfree(rel_head);
>> -			return -ENOMEM;
>> -		}
>> -
>> -		INIT_LIST_HEAD(rel_head->rel_entry);
>> +		INIT_LIST_HEAD(&rel_head->rel_entry);
>>  		rel_head->location = location;
>>  		INIT_HLIST_NODE(&rel_head->node);
>>  		if (!current_head->first) {
>> @@ -722,7 +713,6 @@ static int add_relocation_to_accumulate(struct module *me, int type,
>>  
>>  			if (!bucket) {
>>  				kfree(entry);
>> -				kfree(rel_head->rel_entry);
>>  				kfree(rel_head);
>>  				return -ENOMEM;
>>  			}
>> @@ -735,7 +725,7 @@ static int add_relocation_to_accumulate(struct module *me, int type,
>>  	}
>>  
>>  	/* Add relocation to head of discovered rel_head */
>> -	list_add_tail(&entry->head, rel_head->rel_entry);
>> +	list_add_tail(&entry->head, &rel_head->rel_entry);
>>  
>>  	return 0;
>>  }
>> -- 
>> 2.45.2
>>
>>
> 
> Other than the commit message change suggestions,
> 
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>