[PATCH] evm: fix writing <securityfs>/evm overflow

From: Mimi Zohar <zohar@linux.ibm.com>
To: linux-integrity@vger.kernel.org
Cc: Mimi Zohar <zohar@linux.ibm.com>,
	Stefan Berger <stefanb@linux.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] evm: fix writing <securityfs>/evm overflow
Date: Thu, 29 Apr 2021 15:53:32 -0400	[thread overview]
Message-ID: <20210429195332.310697-1-zohar@linux.ibm.com> (raw)

EVM_SETUP_COMPLETE is defined as 0x80000000, which is larger than INT_MAX.
The "-fno-strict-overflow" compiler option properly prevents signaling
EVM that the EVM policy setup is complete.  Define and read an unsigned
int.

Fixes: f00d79750712 ("EVM: Allow userspace to signal an RSA key has been
loaded")
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/evm/evm_secfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index bbc85637e18b..0007d3362754 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -66,12 +66,13 @@ static ssize_t evm_read_key(struct file *filp, char __user *buf,
 static ssize_t evm_write_key(struct file *file, const char __user *buf,
 			     size_t count, loff_t *ppos)
 {
-	int i, ret;
+	unsigned int i;
+	int ret;
 
 	if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
 		return -EPERM;
 
-	ret = kstrtoint_from_user(buf, count, 0, &i);
+	ret = kstrtouint_from_user(buf, count, 0, &i);
 
 	if (ret)
 		return ret;
-- 
2.27.0

