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

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Date:	Mon, 21 Dec 2015 01:03:26 +0100
From:	Mickaël Salaün <mic@...ikod.net>
To:	linux-kernel@...r.kernel.org
Cc:	Mickaël Salaün <mic@...ikod.net>,
	Jonathan Corbet <corbet@....net>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	Shuah Khan <shuahkh@....samsung.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Hogan <james.hogan@...tec.com>,
	Thomas Meyer <thomas@...3r.de>,
	Nicolas Iooss <nicolas.iooss_linux@....org>,
	Anton Ivanov <aivanov@...cade.com>, linux-doc@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net,
	user-mode-linux-user@...ts.sourceforge.net,
	linux-api@...r.kernel.org,
	Meredydd Luff <meredydd@...atehouse.org>,
	David Drysdale <drysdale@...gle.com>
Subject: [PATCH v1 1/4] um: Fix ptrace GETREGS/SETREGS bugs

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@...ikod.net>
Cc: Jeff Dike <jdike@...toit.com>
Cc: Richard Weinberger <richard@....at>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Will Drewry <wad@...omium.org>
Cc: Thomas Meyer <thomas@...3r.de>
Cc: Nicolas Iooss <nicolas.iooss_linux@....org>
Cc: Anton Ivanov <aivanov@...cade.com>
Cc: linux-kernel@...r.kernel.org
Cc: user-mode-linux-devel@...ts.sourceforge.net
Cc: user-mode-linux-user@...ts.sourceforge.net
Cc: Meredydd Luff <meredydd@...atehouse.org>
Cc: David Drysdale <drysdale@...gle.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

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