ima: Fix a potential integer overflow in ima_appraise_measurement

stable inclusion
from stable-v5.10.132
commit 831e190175f10652be93b08436cc7bf2e62e4bb6
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YS3T

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=831e190175f10652be93b08436cc7bf2e62e4bb6



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[ Upstream commit d2ee2cfc ]

When the ima-modsig is enabled, the rc passed to evm_verifyxattr() may be
negative, which may cause the integer overflow problem.

Fixes: 39b07096 ("ima: Implement support for module-style appended signatures")
Signed-off-by: Huaxin Lu <luhuaxin1@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>