Re: [PATCH] evm: zero-initialize the evm_xattrs read buffer

[Roberto Sassu]

On Tue, 2026-04-07 at 14:09 +0800, Pengpeng Hou wrote:
> evm_read_xattrs() allocates size + 1 bytes, fills them from the list of
> enabled xattrs and then passes strlen(temp) to simple_read_from_buffer().
> When no configured xattrs are enabled, the fill loop stores nothing and
> temp[0] remains uninitialized, so strlen() reads beyond initialized
> memory.
> 
> Use kzalloc() so the empty-list case stays a valid empty C string.

Please also add the Fixes: tag with the relevant commit.

> Signed-off-by: Pengpeng Hou <pengpeng@xxxxxxxxxxx>
> ---
>  security/integrity/evm/evm_secfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
> index acd840461902..03d376fa36c2 100644
> --- a/security/integrity/evm/evm_secfs.c
> +++ b/security/integrity/evm/evm_secfs.c
> @@ -145,7 +145,7 @@ static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
>  		size += strlen(xattr->name) + 1;
>  	}
>  
> -	temp = kmalloc(size + 1, GFP_KERNEL);
> +	temp = kzalloc(size + 1, GFP_KERNEL);

Yes, or just set temp[size] to the terminator so that we don't waste
computation. Can you also change sprintf() to snprintf()?

Thanks

Roberto

>  	if (!temp) {
>  		mutex_unlock(&xattr_list_mutex);
>  		return -ENOMEM;