On Tue, 28 Mar 2017, Dmitry Safonov wrote:
> On 03/22/2017 01:21 AM, Thomas Gleixner wrote:
> > On Tue, 21 Mar 2017, Dmitry Safonov wrote:
> > > v3:
> > > - clear x32 syscall flag during x32 -> x86-64 exec() (thanks, HPA).
> >
> > For correctness sake, this wants to be cleared in the IA32 path as
> > well. It's not causing any harm, but ....
> >
> > I'll amend the patch.
>
> So, just a gentle reminder about this problem.
> Should I resend v4 with clearing x32 bit in ia32 path?
> Or should I resend with this fixup:
> https://lkml.org/lkml/2017/3/22/343
>
> The fixup doesn't look as simple as clearing x32 syscall bit, but I may
> be wrong.
Something like the below should set it correctly for all possible
scenarios.
Thanks,
tglx
8<------------------
arch/x86/kernel/process_64.c | 63 ++++++++++++++++++++++++++++---------------
1 file changed, 42 insertions(+), 21 deletions(-)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -494,6 +494,8 @@ void set_personality_64bit(void)
clear_thread_flag(TIF_IA32);
clear_thread_flag(TIF_ADDR32);
clear_thread_flag(TIF_X32);
+ /* Pretend that this comes from a 64bit execve */
+ task_pt_regs(current)->orig_ax = __NR_execve;
/* Ensure the corresponding mm is not marked. */
if (current->mm)
@@ -506,32 +508,51 @@ void set_personality_64bit(void)
current->personality &= ~READ_IMPLIES_EXEC;
}
-void set_personality_ia32(bool x32)
+static void __set_personality_x32(void)
+{
+#ifdef CONFIG_X86_X32
+ clear_thread_flag(TIF_IA32);
+ set_thread_flag(TIF_X32);
+ if (current->mm)
+ current->mm->context.ia32_compat = TIF_X32;
+ current->personality &= ~READ_IMPLIES_EXEC;
+ /*
+ * in_compat_syscall() uses the presence of the x32
+ * syscall bit flag to determine compat status.
+ * The x86 mmap() code relies on the syscall bitness
+ * so set x32 syscall bit right here to make
+ * in_compat_syscall() work during exec().
+ *
+ * Pretend to come from a x32 execve.
+ */
+ task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT;
+ current->thread.status &= ~TS_COMPAT;
+#endif
+}
+
+static void __set_personality_ia32(void)
{
- /* inherit personality from parent */
+#ifdef CONFIG_COMPAT_32
+ set_thread_flag(TIF_IA32);
+ clear_thread_flag(TIF_X32);
+ if (current->mm)
+ current->mm->context.ia32_compat = TIF_IA32;
+ current->personality |= force_personality32;
+ /* Prepare the first "return" to user space */
+ task_pt_regs(current)->orig_ax = __NR_ia32_execve;
+ current->thread.status |= TS_COMPAT;
+#endif
+}
+void set_personality_ia32(bool x32)
+{
/* Make sure to be in 32bit mode */
set_thread_flag(TIF_ADDR32);
- /* Mark the associated mm as containing 32-bit tasks. */
- if (x32) {
- clear_thread_flag(TIF_IA32);
- set_thread_flag(TIF_X32);
- if (current->mm)
- current->mm->context.ia32_compat = TIF_X32;
- current->personality &= ~READ_IMPLIES_EXEC;
- /* in_compat_syscall() uses the presence of the x32
- syscall bit flag to determine compat status */
- current->thread.status &= ~TS_COMPAT;
- } else {
- set_thread_flag(TIF_IA32);
- clear_thread_flag(TIF_X32);
- if (current->mm)
- current->mm->context.ia32_compat = TIF_IA32;
- current->personality |= force_personality32;
- /* Prepare the first "return" to user space */
- current->thread.status |= TS_COMPAT;
- }
+ if (x32)
+ __set_personality_x32();
+ else
+ __set_personality_ia32();
}
EXPORT_SYMBOL_GPL(set_personality_ia32);
