2021-04-29 20:15:14

by Mimi Zohar

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

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 <[email protected]>
---
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

2021-04-29 20:32:11

by Stefan Berger

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

On 4/29/21 3:53 PM, Mimi Zohar wrote:
> 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 <[email protected]>


Tested-by: Stefan Berger <[email protected]>

> ---
> 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;