ia64 has two stacks:
- memory stack (or stack), pointed at by by r12
- register backing store (register stack), pointed at
ar.bsp/ar.bspstore with complications around dirty
register frame on CPU.
In https://bugs.gentoo.org/769614 Dmitry noticed that
PTRACE_GET_SYSCALL_INFO returns register stack instead
memory stack.
The bug comes from the fact that user_stack_pointer() and
current_user_stack_pointer() don't return the same register:
ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; }
#define current_user_stack_pointer() (current_pt_regs()->r12)
The change gets both back in sync.
I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user
by this bug on ia64.
The change fixes 'rt_sigreturn.gen.test' strace test where
it was observed initially.
CC: Andrew Morton <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: [email protected]
Bug: https://bugs.gentoo.org/769614
Reported-by: Dmitry V. Levin <[email protected]>
Signed-off-by: Sergei Trofimovich <[email protected]>
---
arch/ia64/include/asm/ptrace.h | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/arch/ia64/include/asm/ptrace.h b/arch/ia64/include/asm/ptrace.h
index b3aa46090101..08179135905c 100644
--- a/arch/ia64/include/asm/ptrace.h
+++ b/arch/ia64/include/asm/ptrace.h
@@ -54,8 +54,7 @@
static inline unsigned long user_stack_pointer(struct pt_regs *regs)
{
- /* FIXME: should this be bspstore + nr_dirty regs? */
- return regs->ar_bspstore;
+ return regs->r12;
}
static inline int is_syscall_success(struct pt_regs *regs)
@@ -79,11 +78,6 @@ static inline long regs_return_value(struct pt_regs *regs)
unsigned long __ip = instruction_pointer(regs); \
(__ip & ~3UL) + ((__ip & 3UL) << 2); \
})
-/*
- * Why not default? Because user_stack_pointer() on ia64 gives register
- * stack backing store instead...
- */
-#define current_user_stack_pointer() (current_pt_regs()->r12)
/* given a pointer to a task_struct, return the user's pt_regs */
# define task_pt_regs(t) (((struct pt_regs *) ((char *) (t) + IA64_STK_OFFSET)) - 1)
--
2.31.1
On Wed, 31 Mar 2021 09:44:47 +0100 Sergei Trofimovich <[email protected]> wrote:
> ia64 has two stacks:
> - memory stack (or stack), pointed at by by r12
> - register backing store (register stack), pointed at
> ar.bsp/ar.bspstore with complications around dirty
> register frame on CPU.
>
> In https://bugs.gentoo.org/769614 Dmitry noticed that
> PTRACE_GET_SYSCALL_INFO returns register stack instead
> memory stack.
>
> The bug comes from the fact that user_stack_pointer() and
> current_user_stack_pointer() don't return the same register:
>
> ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; }
> #define current_user_stack_pointer() (current_pt_regs()->r12)
>
> The change gets both back in sync.
>
> I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user
> by this bug on ia64.
>
> The change fixes 'rt_sigreturn.gen.test' strace test where
> it was observed initially.
>
I assume a cc:stable is justified here?
The bug seems to have been there for 10+ years, so there isn't a lot of
point in looking for the Fixes: reference.
On Wed, 31 Mar 2021 17:49:08 -0700
Andrew Morton <[email protected]> wrote:
> On Wed, 31 Mar 2021 09:44:47 +0100 Sergei Trofimovich <[email protected]> wrote:
>
> > ia64 has two stacks:
> > - memory stack (or stack), pointed at by by r12
> > - register backing store (register stack), pointed at
> > ar.bsp/ar.bspstore with complications around dirty
> > register frame on CPU.
> >
> > In https://bugs.gentoo.org/769614 Dmitry noticed that
> > PTRACE_GET_SYSCALL_INFO returns register stack instead
> > memory stack.
> >
> > The bug comes from the fact that user_stack_pointer() and
> > current_user_stack_pointer() don't return the same register:
> >
> > ulong user_stack_pointer(struct pt_regs *regs) { return regs->ar_bspstore; }
> > #define current_user_stack_pointer() (current_pt_regs()->r12)
> >
> > The change gets both back in sync.
> >
> > I think ptrace(PTRACE_GET_SYSCALL_INFO) is the only affected user
> > by this bug on ia64.
> >
> > The change fixes 'rt_sigreturn.gen.test' strace test where
> > it was observed initially.
> >
>
> I assume a cc:stable is justified here?
>
> The bug seems to have been there for 10+ years, so there isn't a lot of
> point in looking for the Fixes: reference.
Yes, I think cc:stable is fine.
--
Sergei