[3.5.y.z extended stable] Patch "ARM: 7851/1: check for number of arguments in" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ARM: 7851/1: check for number of arguments in

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2b7337ca7c07f0ac2932816bd9453f42fb2fb451 Mon Sep 17 00:00:00 2001
From: AKASHI Takahiro <takahiro.akashi at linaro.org>
Date: Wed, 9 Oct 2013 15:58:29 +0100
Subject: [PATCH] ARM: 7851/1: check for number of arguments in
 syscall_get/set_arguments()

commit 3c1532df5c1b54b5f6246cdef94eeb73a39fe43a upstream.

In ftrace_syscall_enter(),
    syscall_get_arguments(..., 0, n, ...)
        if (i == 0) { <handle ORIG_r0> ...; n--;}
        memcpy(..., n * sizeof(args[0]));
If 'number of arguments(n)' is zero and 'argument index(i)' is also zero in
syscall_get_arguments(), none of arguments should be copied by memcpy().
Otherwise 'n--' can be a big positive number and unexpected amount of data
will be copied. Tracing system calls which take no argument, say sync(void),
may hit this case and eventually make the system corrupted.
This patch fixes the issue both in syscall_get_arguments() and
syscall_set_arguments().

Acked-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm/include/asm/syscall.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index fce38a6..36b69df 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -51,6 +51,9 @@ static inline void syscall_get_arguments(struct task_struct *task,
 					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
+	if (n == 0)
+		return;
+
 	if (i + n > SYSCALL_MAX_ARGS) {
 		unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i;
 		unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
@@ -75,6 +78,9 @@ static inline void syscall_set_arguments(struct task_struct *task,
 					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
+	if (n == 0)
+		return;
+
 	if (i + n > SYSCALL_MAX_ARGS) {
 		pr_warning("%s called with max args %d, handling only %d\n",
 			   __func__, i + n, SYSCALL_MAX_ARGS);
--
1.8.3.2