af_key: Fix send_acquire race with pfkey_register

stable inclusion
from stable-v5.10.157
commit b7000254c12537ea63d9304ac8b2f5379fdc258e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MU59

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7000254c12537ea63d9304ac8b2f5379fdc258e



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[ Upstream commit 7f57f816 ]

The function pfkey_send_acquire may race with pfkey_register
(which could even be in a different name space).  This may result
in a buffer overrun.

Allocating the maximum amount of memory that could be used prevents
this.

Reported-by:  <syzbot+1e9af9185d8850e2c2fa@syzkaller.appspotmail.com>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>