net: switch to storing KCOV handle directly in sk_buff

stable inclusion
from stable-v5.10.163
commit 67349025f00d0749e36386cfcfc32c2887f47fdb
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6D0MR
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=67349025f00d0749e36386cfcfc32c2887f47fdb

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

[ Upstream commit fa69ee5a ]

It turns out that usage of skb extensions can cause memory leaks. Ido
Schimmel reported: "[...] there are instances that blindly overwrite
'skb->extensions' by invoking skb_copy_header() after __alloc_skb()."

Therefore, give up on using skb extensions for KCOV handle, and instead
directly store kcov_handle in sk_buff.

Fixes: 6370cc3b ("net: add kcov handle to skb extensions")
Fixes: 85ce50d3 ("net: kcov: don't select SKB_EXTENSIONS when there is no NET")
Fixes: 97f53a08 ("net: linux/skbuff.h: combine SKB_EXTENSIONS + KCOV handling")
Link: https://lore.kernel.org/linux-wireless/20201121160941.GA485907@shredder.lan/


Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20201125224840.2014773-1-elver@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: db0b124f ("igc: Enhance Qbv scheduling by using first flag bit")
Signed-off-by: Sasha Levin <sashal@kernel.org>

Conflicts:
	include/linux/skbuff.h

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Liu Jian <liujian56@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
(cherry picked from commit 1cc9c0b2)