NACK/cmnt: [PATCH][SRU][X] ethtool: do not vzalloc(0) on registers dump

[Kleber Souza]

On 07/12/17 20:40, Eric Desrochers wrote:
> From: Stanislaw Gruszka <sgruszka at redhat.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1703944
> 
> If ->get_regs_len() callback return 0, we allocate 0 bytes of memory,
> what print ugly warning in dmesg, which can be found further below.
> 
> This happen on mac80211 devices where ieee80211_get_regs_len() just
> return 0 and driver only fills ethtool_regs structure and actually
> do not provide any dump. However I assume this can happen on other
> drivers i.e. when for some devices driver provide regs dump and for
> others do not. Hence preventing to to print warning in ethtool code
> seems to be reasonable.
> 
> ethtool: vmalloc: allocation failure: 0 bytes, mode:0x24080c2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_ZERO)
> <snip>
> Call Trace:
> [<ffffffff813bde47>] dump_stack+0x63/0x8c
> [<ffffffff811b0a1f>] warn_alloc+0x13f/0x170
> [<ffffffff811f0476>] __vmalloc_node_range+0x1e6/0x2c0
> [<ffffffff811f0874>] vzalloc+0x54/0x60
> [<ffffffff8169986c>] dev_ethtool+0xb4c/0x1b30
> [<ffffffff816adbb1>] dev_ioctl+0x181/0x520
> [<ffffffff816714d2>] sock_do_ioctl+0x42/0x50
> <snip>
> Mem-Info:
> active_anon:435809 inactive_anon:173951 isolated_anon:0
> active_file:835822 inactive_file:196932 isolated_file:0
> unevictable:0 dirty:8 writeback:0 unstable:0
> slab_reclaimable:157732 slab_unreclaimable:10022
> mapped:83042 shmem:306356 pagetables:9507 bounce:0
> free:130041 free_pcp:1080 free_cma:0
> Node 0 active_anon:1743236kB inactive_anon:695804kB active_file:3343288kB inactive_file:787728kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:332168kB dirty:32kB writeback:0kB shmem:0kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 1225424kB writeback_tmp:0kBunstable:0kB pages_scanned:0 all_unreclaimable? no
> Node 0 DMA free:15900kB min:136kB low:168kB high:200kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15984kB managed:15900kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kBbounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> lowmem_reserve[]: 0 3187 7643 7643
> Node 0 DMA32 free:419732kB min:28124kB low:35152kB high:42180kB active_anon:541180kB inactive_anon:248988kB active_file:1466388kB inactive_file:389632kB unevictable:0kB writepending:0kB present:3370280kB managed:3290932kB mlocked:0kB slab_reclaimable:217184kB slab_unreclaimable:4180kB kernel_stack:160kB pagetables:984kB bounce:0kB free_pcp:2236kB local_pcp:660kB free_cma:0kB
> lowmem_reserve[]: 0 0 4456 4456
> 
> Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from commit 3808d34838184fd29088d6b3a364ba2f1c018fb6)
> Signed-off-by: Eric Desrochers <eric.desrochers at canonical.com>
> 
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index d1e4995..e3048cf 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1369,9 +1369,12 @@ static int ethtool_get_regs(struct net_device *dev, char __user *useraddr)
>  	if (regs.len > reglen)
>  		regs.len = reglen;
>  
> -	regbuf = vzalloc(reglen);
> -	if (reglen && !regbuf)
> -		return -ENOMEM;
> +	regbuf = NULL;
> +	if (reglen) {
> +		regbuf = vzalloc(reglen);
> +		if (!regbuf)
> +			return -ENOMEM;
> +	}
>  
>  	ops->get_regs(dev, &regs, regbuf);
>  
> 

Patch was already applied as part of Xenial update to 4.4.73 stable
release (LP #1698817).