Commit cee069c9 authored by Dianzhang Chen's avatar Dianzhang Chen Committed by Kleber Sacilotto de Souza

x86/tls: Fix possible spectre-v1 in do_get_thread_area()

BugLink: https://bugs.launchpad.net/bugs/1838467

commit 993773d1 upstream.

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 index can be controlled from:
        ptrace -> arch_ptrace -> do_get_thread_area.

Fix this by sanitizing the user supplied index before using it to access
the p->thread.tls_array.
Signed-off-by: default avatarDianzhang Chen <dianzhangchen0@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: bp@alien8.de
Cc: hpa@zytor.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1561524630-3642-1-git-send-email-dianzhangchen0@gmail.comSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarConnor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: default avatarKhalid Elmously <khalid.elmously@canonical.com>
parent 3390107c
...@@ -4,6 +4,7 @@ ...@@ -4,6 +4,7 @@
#include <linux/user.h> #include <linux/user.h>
#include <linux/regset.h> #include <linux/regset.h>
#include <linux/syscalls.h> #include <linux/syscalls.h>
#include <linux/nospec.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
#include <asm/desc.h> #include <asm/desc.h>
...@@ -177,6 +178,7 @@ int do_get_thread_area(struct task_struct *p, int idx, ...@@ -177,6 +178,7 @@ int do_get_thread_area(struct task_struct *p, int idx,
struct user_desc __user *u_info) struct user_desc __user *u_info)
{ {
struct user_desc info; struct user_desc info;
int index;
if (idx == -1 && get_user(idx, &u_info->entry_number)) if (idx == -1 && get_user(idx, &u_info->entry_number))
return -EFAULT; return -EFAULT;
...@@ -184,8 +186,11 @@ int do_get_thread_area(struct task_struct *p, int idx, ...@@ -184,8 +186,11 @@ int do_get_thread_area(struct task_struct *p, int idx,
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL; return -EINVAL;
fill_user_desc(&info, idx, index = idx - GDT_ENTRY_TLS_MIN;
&p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]); index = array_index_nospec(index,
GDT_ENTRY_TLS_MAX - GDT_ENTRY_TLS_MIN + 1);
fill_user_desc(&info, idx, &p->thread.tls_array[index]);
if (copy_to_user(u_info, &info, sizeof(info))) if (copy_to_user(u_info, &info, sizeof(info)))
return -EFAULT; return -EFAULT;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment