Re: [RESEND RFC] kernel/ksysfs.c: restrict /sys/kernel/notes to root access

[Greg KH <gregkh@linuxfoundation.org>]

On Sat, Feb 17, 2024 at 10:19:32PM -0800, Guixiong Wei wrote:
> Restrict non-privileged user access to /sys/kernel/notes to
> avoid security attack.
> 
> The non-privileged users have read access to notes. The notes
> expose the load address of startup_xen. This address could be
> used to bypass KASLR.
> 
> For example, the startup_xen is built at 0xffffffff82465180 and
> commit_creds is built at 0xffffffff810ad570 which could read from
> the /boot/System.map. And the loaded address of startup_xen is
> 0xffffffffbc265180 which read from /sys/kernel/notes. So the loaded
> address of commit_creds is 0xffffffffbc265180 - (0xffffffff82465180
> - 0xffffffff810ad570) = 0xffffffffbaead570.
> 
> Signed-off-by: Guixiong Wei
> ---
> kernel/ksysfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
> index 1d4bc493b2f4..ccef642dc4c6 100644
> --- a/kernel/ksysfs.c
> +++ b/kernel/ksysfs.c
> @@ -241,7 +241,7 @@ static ssize_t notes_read(struct file *filp, struct
> kobject *kobj,
> static struct bin_attribute notes_attr __ro_after_init = {
> .attr = {
> .name = "notes",
> - .mode = S_IRUGO,
> + .mode = S_IRUSR,
> },
> .read = &notes_read,
> };
> -- 
> 2.20.1

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