[PATCH 4.19 101/421] evm: fix writing /evm overflow

Greg Kroah-Hartman
2021-07-19T16:08:02Z

From: Mimi Zohar <zohar@linux.ibm.com>

[ Upstream commit 49219d9b8785ba712575c40e48ce0f7461254626 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 7024b14831e3..c5c44203a59c 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -71,12 +71,13 @@ 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;
--
2.30.2