[PATCH v1 1/4] um: Fix ptrace GETREGS/SETREGS bugs

Mickaël Salaün
2015-12-21T00:18:06Z

This fix two related bugs:
* PTRACE_GETREGS doesn't get the right orig_ax (syscall) value
* PTRACE_SETREGS can't set the orig_ax value (erased by initial value)

Remove the now useless and error-prone get_syscall().

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: Thomas Meyer <thomas@m3y3r.de>
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Anton Ivanov <aivanov@brocade.com>
Cc: linux-kernel@vger.kernel.org
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: David Drysdale <drysdale@google.com>
---
arch/um/kernel/skas/syscall.c | 7 ++++++-
arch/um/os-Linux/skas/process.c | 7 -------
2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 1683b8e..65f0d1a 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -7,6 +7,7 @@
#include <linux/ptrace.h>
#include <kern_util.h>
#include <sysdep/ptrace.h>
+#include <sysdep/ptrace_user.h>
#include <sysdep/syscalls.h>
#include <os.h>

@@ -16,12 +17,16 @@ void handle_syscall(struct uml_pt_regs *r)
long result;
int syscall;

+ /* Save the syscall register. */
+ UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
+
if (syscall_trace_enter(regs)) {
result = -ENOSYS;
goto out;
}

- syscall = get_syscall(r);
+ /* Get the syscall after being potentially updated with ptrace. */
+ syscall = UPT_SYSCALL_NR(r);

if ((syscall > __NR_syscall_max) || syscall < 0)
result = -ENOSYS;
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index b856c66..23025d6 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -172,13 +172,6 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
handle_syscall(regs);
}

-int get_syscall(struct uml_pt_regs *regs)
-{
- UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
-
- return UPT_SYSCALL_NR(regs);
-}
-
extern char __syscall_stub_start[];

static int userspace_tramp(void *stack)
--
2.6.4