linux-kernel - [PATCH v2] powerpc/uaccess: fix warning/error with access

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Message-Id: <a56d58b1d98ef47461b72ff94380c4e2dd953fd1.1539855545.git.christophe.leroy@c-s.fr>
Date:   Thu, 18 Oct 2018 09:40:34 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2] powerpc/uaccess: fix warning/error with access_ok()

With the following peace of code, the following compilation warning
is encountered:

	if (_IOC_DIR(ioc) != _IOC_NONE) {
		int verify = _IOC_DIR(ioc) & _IOC_READ ? VERIFY_WRITE : VERIFY_READ;

		if (!access_ok(verify, ioarg, _IOC_SIZE(ioc))) {

drivers/platform/test/dev.c: In function ‘my_ioctl’:
drivers/platform/test/dev.c:219:7: warning: unused variable ‘verify’ [-Wunused-variable]
   int verify = _IOC_DIR(ioc) & _IOC_READ ? VERIFY_WRITE : VERIFY_READ;

This patch fixes it by handing the type to __access_ok(), changing it
to an inline function for PPC64 as already done for PPC32

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 v2: fixed the three direct users of __access_ok()

 arch/powerpc/include/asm/uaccess.h | 13 ++++++++-----
 arch/powerpc/kernel/process.c      |  2 +-
 arch/powerpc/lib/sstep.c           |  4 ++--
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 15bea9a0f260..97faf0353919 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -47,13 +47,16 @@ static inline void set_fs(mm_segment_t fs)
  * This check is sufficient because there is a large enough
  * gap between user addresses and the kernel addresses
  */
-#define __access_ok(addr, size, segment)	\
-	(((addr) <= (segment).seg) && ((size) <= (segment).seg))
+static inline int __access_ok(int type, unsigned long addr, unsigned long size,
+			      mm_segment_t seg)
+{
+	return addr <= seg.seg && size <= seg.seg;
+}
 
 #else
 
-static inline int __access_ok(unsigned long addr, unsigned long size,
-			mm_segment_t seg)
+static inline int __access_ok(int type, unsigned long addr, unsigned long size,
+			      mm_segment_t seg)
 {
 	if (addr > seg.seg)
 		return 0;
@@ -64,7 +67,7 @@ static inline int __access_ok(unsigned long addr, unsigned long size,
 
 #define access_ok(type, addr, size)		\
 	(__chk_user_ptr(addr),			\
-	 __access_ok((__force unsigned long)(addr), (size), get_fs()))
+	 __access_ok((type), (__force unsigned long)(addr), (size), get_fs()))
 
 /*
  * These are the main single-value transfer routines.  They automatically
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 7ad304a3cc7d..4cc84fe13f9c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1310,7 +1310,7 @@ void show_user_instructions(struct pt_regs *regs)
 	 * Make sure the NIP points at userspace, not kernel text/data or
 	 * elsewhere.
 	 */
-	if (!__access_ok(pc, NR_INSN_TO_PRINT * sizeof(int), USER_DS)) {
+	if (!__access_ok(VERIFY_READ, pc, NR_INSN_TO_PRINT * sizeof(int), USER_DS)) {
 		pr_info("%s[%d]: Bad NIP, not dumping instructions.\n",
 			current->comm, current->pid);
 		return;
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index d81568f783e5..ff117418257c 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -110,9 +110,9 @@ static nokprobe_inline long address_ok(struct pt_regs *regs,
 {
 	if (!user_mode(regs))
 		return 1;
-	if (__access_ok(ea, nb, USER_DS))
+	if (__access_ok(VERIFY_WRITE, ea, nb, USER_DS))
 		return 1;
-	if (__access_ok(ea, 1, USER_DS))
+	if (__access_ok(VERIFY_WRITE, ea, 1, USER_DS))
 		/* Access overlaps the end of the user region */
 		regs->dar = USER_DS.seg;
 	else
-- 
2.13.3