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

[Eric Dumazet]

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 ?

>   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@xxxxxxxxxxxxxx>
> ---
>  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);
>  }
>  
>