On Wed, Jun 26, 2019 at 12:38 AM Thomas Gleixner <t...@linutronix.de> wrote: > > 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 >
sorry for being careless, my bad. And thanks for suggestion, i'll fix that in next version.