linux-kernel - [PATCH 4.4 08/14] mips/ptrace: Preserve previous registers for short regset write

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Message-Id: <20170330094946.295768475@linuxfoundation.org>
Date:   Thu, 30 Mar 2017 11:58:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.4 08/14] mips/ptrace: Preserve previous registers for short regset write

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Martin <Dave.Martin@....com>

commit d614fd58a2834cfe4efa472c33c8f3ce2338b09b upstream.

Ensure that if userspace supplies insufficient data to PTRACE_SETREGSET
to fill all the registers, the thread's old registers are preserved.

Signed-off-by: Dave Martin <Dave.Martin@....com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/ptrace.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -485,7 +485,8 @@ static int fpr_set(struct task_struct *t
 					  &target->thread.fpu,
 					  0, sizeof(elf_fpregset_t));
 
-	for (i = 0; i < NUM_FPU_REGS; i++) {
+	BUILD_BUG_ON(sizeof(fpr_val) != sizeof(elf_fpreg_t));
+	for (i = 0; i < NUM_FPU_REGS && count >= sizeof(elf_fpreg_t); i++) {
 		err = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 					 &fpr_val, i * sizeof(elf_fpreg_t),
 					 (i + 1) * sizeof(elf_fpreg_t));