ipv6: sr: fix memleak in seg6_hmac_init_algo

stable inclusion
from stable-v4.19.316
commit afd5730969aec960a2fee4e5ee839a6014643976
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAC3N0
CVE: CVE-2024-39489

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=afd5730969aec960a2fee4e5ee839a6014643976



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

[ Upstream commit efb9f4f19f8e37fde43dfecebc80292d179f56c6 ]

seg6_hmac_init_algo returns without cleaning up the previous allocations
if one fails, so it's going to leak all that memory and the crypto tfms.

Update seg6_hmac_exit to only free the memory when allocated, so we can
reuse the code directly.

Fixes: bf355b8d ("ipv6: sr: add core files for SR HMAC support")
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Closes: https://lore.kernel.org/netdev/Zj3bh-gE7eT6V6aH@hog/


Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/20240517005435.2600277-1-liuhangbin@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>