Messages in this thread Patch in this message | | | Date | Tue, 25 Jun 2019 18:37:58 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] x86/tls: Fix possible spectre-v1 in do_get_thread_area() |
| |
On Wed, 26 Jun 2019, Dianzhang Chen wrote:
> The index to access the threads tls array is controlled by userspace > via syscall: sys_ptrace(), hence leading to a potential exploitation > of the Spectre variant 1 vulnerability. > The idx can be controlled from: > ptrace -> arch_ptrace -> do_get_thread_area. > > Fix this by sanitizing idx before using it to index p->thread.tls_array.
Just that I can't find a place which sanitizes the value....
> +#include <linux/nospec.h>
and nothing which uses anything from this header file.
> #include <linux/uaccess.h> > #include <asm/desc.h> > @@ -220,6 +221,7 @@ int do_get_thread_area(struct task_struct *p, int idx, > struct user_desc __user *u_info) > { > struct user_desc info; > + int index; > > if (idx == -1 && get_user(idx, &u_info->entry_number)) > return -EFAULT; > @@ -227,8 +229,9 @@ int do_get_thread_area(struct task_struct *p, int idx, > if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) > return -EINVAL; > > - fill_user_desc(&info, idx, > - &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]); > + index = idx - GDT_ENTRY_TLS_MIN; > + > + fill_user_desc(&info, idx, &p->thread.tls_array[index]);
So this is just a cosmetic change and the compiler will create probably exactly the same binary.
Thanks,
tglx
| |