sfc_ef100: potential dereference of null pointer

stable inclusion
from stable-v5.10.88
commit 734a3f3106053ee41cecae2a995b3d4d0c246764
bugzilla: 186058 https://gitee.com/openeuler/kernel/issues/I4QW6A

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=734a3f3106053ee41cecae2a995b3d4d0c246764

--------------------------------

[ Upstream commit 407ecd1b ]

The return value of kmalloc() needs to be checked.
To avoid use in efx_nic_update_stats() in case of the failure of alloc.

Fixes: b593b6f1 ("sfc_ef100: statistics gathering")
Signed-off-by: NJiasheng Jiang <jiasheng@iscas.ac.cn>
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/sfc/ef100_nic.c

@@ -597,6 +597,9 @@ static size_t ef100_update_stats(struct efx_nic *efx,
 	ef100_common_stat_mask(mask);
 	ef100_ethtool_stat_mask(mask);
 
+	if (!mc_stats)
+		return 0;
+
 	efx_nic_copy_stats(efx, mc_stats);
 	efx_nic_update_stats(ef100_stat_desc, EF100_STAT_COUNT, mask,
 			     stats, mc_stats, false);