commit 502585c7555083d4a949c08350306b9ec196779e
author Dave Martin <Dave.Martin@arm.com> Mon Mar 27 15:10:54 2017 +0100
committer Linus Torvalds <torvalds@linux-foundation.org> Wed Mar 29 08:54:17 2017 -0700
tree ceadf8d793ceaae32940754291fbd056a7cfa2ce
parent fb411b837b587a32046dc4f369acb93a10b1def8

h8300/ptrace: Fix incorrect register transfer count

regs_set() and regs_get() are vulnerable to an off-by-1 buffer overrun
if CONFIG_CPU_H8S is set, since this adds an extra entry to
register_offset[] but not to user_regs_struct.

So, iterate over user_regs_struct based on its actual size, not based on
the length of register_offset[].

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/h8300/kernel/ptrace.c

diff --git a/arch/h8300/kernel/ptrace.c b/arch/h8300/kernel/ptrace.c
index 9207554..0dc1c8f 100644
--- a/arch/h8300/kernel/ptrace.c
+++ b/arch/h8300/kernel/ptrace.c
@@ -95,7 +95,8 @@
 	long *reg = (long *)&regs;
 
 	/* build user regs in buffer */
-	for (r = 0; r < ARRAY_SIZE(register_offset); r++)
+	BUILD_BUG_ON(sizeof(regs) % sizeof(long) != 0);
+	for (r = 0; r < sizeof(regs) / sizeof(long); r++)
 		*reg++ = h8300_get_reg(target, r);
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
@@ -113,7 +114,8 @@
 	long *reg;
 
 	/* build user regs in buffer */
-	for (reg = (long *)&regs, r = 0; r < ARRAY_SIZE(register_offset); r++)
+	BUILD_BUG_ON(sizeof(regs) % sizeof(long) != 0);
+	for (reg = (long *)&regs, r = 0; r < sizeof(regs) / sizeof(long); r++)
 		*reg++ = h8300_get_reg(target, r);
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
@@ -122,7 +124,7 @@
 		return ret;
 
 	/* write back to pt_regs */
-	for (reg = (long *)&regs, r = 0; r < ARRAY_SIZE(register_offset); r++)
+	for (reg = (long *)&regs, r = 0; r < sizeof(regs) / sizeof(long); r++)
 		h8300_put_reg(target, r, *reg++);
 	return 0;
 }