linux-kernel - Re: [PATCH] net/core/neighbour: tell kmemleak about hash tables

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Date:   Tue, 8 Jan 2019 15:56:21 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/core/neighbour: tell kmemleak about hash tables



On 08.01.2019 14:59, Eric Dumazet wrote:
> 
> 
> On 01/08/2019 01:30 AM, Konstantin Khlebnikov wrote:
>> This fixes false-positive kmemleak reports about leaked neighbour entries:
>>
>> unreferenced object 0xffff8885c6e4d0a8 (size 1024):
> 
> 
> size 1024 object : should have been allocated by kzalloc(), right ?

Yep, neigh_alloc calls kzalloc.

Size might be bloated by lockdep.

> 
>>    comm "softirq", pid 0, jiffies 4294922664 (age 167640.804s)
>>    hex dump (first 32 bytes):
>>      00 00 00 00 00 00 00 00 20 2c f3 83 ff ff ff ff  ........ ,......
>>      08 c0 ef 5f 84 88 ff ff 01 8c 7d 02 01 00 00 00  ..._......}.....
>>    backtrace:
>>      [<00000000748509fe>] ip6_finish_output2+0x887/0x1e40
>>      [<0000000036d7a0d8>] ip6_output+0x1ba/0x600
>>      [<0000000027ea7dba>] ip6_send_skb+0x92/0x2f0
>>      [<00000000d6e2111d>] udp_v6_send_skb.isra.24+0x680/0x15e0
>>      [<000000000668a8be>] udpv6_sendmsg+0x18c9/0x27a0
>>      [<000000004bd5fa90>] sock_sendmsg+0xb3/0xf0
>>      [<000000008227b29f>] ___sys_sendmsg+0x745/0x8f0
>>      [<000000008698009d>] __sys_sendmsg+0xde/0x170
>>      [<00000000889dacf1>] do_syscall_64+0x9b/0x400
>>      [<0000000081cdb353>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>      [<000000005767ed39>] 0xffffffffffffffff
>>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>> ---
>>   net/core/neighbour.c |   13 +++++++++----
>>   1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
>> index 763a7b08df67..3e27a779f288 100644
>> --- a/net/core/neighbour.c
>> +++ b/net/core/neighbour.c
>> @@ -18,6 +18,7 @@
>>   #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>>   
>>   #include <linux/slab.h>
>> +#include <linux/kmemleak.h>
>>   #include <linux/types.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>> @@ -443,12 +444,14 @@ static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
>>   	ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
>>   	if (!ret)
>>   		return NULL;
>> -	if (size <= PAGE_SIZE)
>> +	if (size <= PAGE_SIZE) {
>>   		buckets = kzalloc(size, GFP_ATOMIC);
>> -	else
>> +	} else {
>>   		buckets = (struct neighbour __rcu **)
>>   			  __get_free_pages(GFP_ATOMIC | __GFP_ZERO,
>>   					   get_order(size));
>> +		kmemleak_alloc(buckets, size, 0, GFP_ATOMIC);
>> +	}
>>   	if (!buckets) {
>>   		kfree(ret);
>>   		return NULL;
>> @@ -468,10 +471,12 @@ static void neigh_hash_free_rcu(struct rcu_head *head)
>>   	size_t size = (1 << nht->hash_shift) * sizeof(struct neighbour *);
>>   	struct neighbour __rcu **buckets = nht->hash_buckets;
>>   
>> -	if (size <= PAGE_SIZE)
>> +	if (size <= PAGE_SIZE) {
>>   		kfree(buckets);
>> -	else
>> +	} else {
>> +		kmemleak_free(buckets);
>>   		free_pages((unsigned long)buckets, get_order(size));
>> +	}
>>   	kfree(nht);
>>   }
>>   
>>