Patch "arm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    arm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-ptrace-reject-attempts-to-set-incomplete-hardware-breakpoint-fields.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ad9e202aa1ce571b1d7fed969d06f66067f8a086 Mon Sep 17 00:00:00 2001
From: Dave Martin <Dave.Martin@arm.com>
Date: Wed, 18 Jan 2017 16:25:24 +0000
Subject: arm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields

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

commit ad9e202aa1ce571b1d7fed969d06f66067f8a086 upstream.

We cannot preserve partial fields for hardware breakpoints, because
the values written by userspace to the hardware breakpoint
registers can't subsequently be recovered intact from the hardware.

So, just reject attempts to write incomplete fields with -EINVAL.

Fixes: 478fcb2cdb23 ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <Will.Deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/kernel/ptrace.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -450,6 +450,8 @@ static int hw_break_set(struct task_stru
 	/* (address, ctrl) registers */
 	limit = regset->n * regset->size;
 	while (count && offset < limit) {
+		if (count < PTRACE_HBP_ADDR_SZ)
+			return -EINVAL;
 		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &addr,
 					 offset, offset + PTRACE_HBP_ADDR_SZ);
 		if (ret)
@@ -459,6 +461,8 @@ static int hw_break_set(struct task_stru
 			return ret;
 		offset += PTRACE_HBP_ADDR_SZ;
 
+		if (!count)
+			break;
 		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl,
 					 offset, offset + PTRACE_HBP_CTRL_SZ);
 		if (ret)


Patches currently in stable-queue which might be from Dave.Martin@arm.com are

queue-4.4/arm64-ptrace-preserve-previous-registers-for-short-regset-write-3.patch
queue-4.4/arm64-ptrace-reject-attempts-to-set-incomplete-hardware-breakpoint-fields.patch
queue-4.4/arm64-ptrace-preserve-previous-registers-for-short-regset-write-2.patch
queue-4.4/arm64-ptrace-avoid-uninitialised-struct-padding-in-fpr_set.patch
queue-4.4/arm64-ptrace-preserve-previous-registers-for-short-regset-write.patch