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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.16 093/279] arm64: ptrace: remove addr_limit manipulation
Date:   Mon, 18 Jun 2018 10:11:18 +0200
Message-Id: <20180618080612.648341955@linuxfoundation.org>
In-Reply-To: <20180618080608.851973560@linuxfoundation.org>
References: <20180618080608.851973560@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Mark Rutland <mark.rutland@arm.com>

[ Upstream commit 59275a0c037ed6fabd6354730f1e3104264ab719 ]

We transiently switch to KERNEL_DS in compat_ptrace_gethbpregs() and
compat_ptrace_sethbpregs(), but in either case this is pointless as we
don't perform any uaccess during this window.

let's rip out the redundant addr_limit manipulation.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/kernel/ptrace.c |    6 ------
 1 file changed, 6 deletions(-)

--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1458,9 +1458,7 @@ static int compat_ptrace_gethbpregs(stru
 {
 	int ret;
 	u32 kdata;
-	mm_segment_t old_fs = get_fs();
 
-	set_fs(KERNEL_DS);
 	/* Watchpoint */
 	if (num < 0) {
 		ret = compat_ptrace_hbp_get(NT_ARM_HW_WATCH, tsk, num, &kdata);
@@ -1471,7 +1469,6 @@ static int compat_ptrace_gethbpregs(stru
 	} else {
 		ret = compat_ptrace_hbp_get(NT_ARM_HW_BREAK, tsk, num, &kdata);
 	}
-	set_fs(old_fs);
 
 	if (!ret)
 		ret = put_user(kdata, data);
@@ -1484,7 +1481,6 @@ static int compat_ptrace_sethbpregs(stru
 {
 	int ret;
 	u32 kdata = 0;
-	mm_segment_t old_fs = get_fs();
 
 	if (num == 0)
 		return 0;
@@ -1493,12 +1489,10 @@ static int compat_ptrace_sethbpregs(stru
 	if (ret)
 		return ret;
 
-	set_fs(KERNEL_DS);
 	if (num < 0)
 		ret = compat_ptrace_hbp_set(NT_ARM_HW_WATCH, tsk, num, &kdata);
 	else
 		ret = compat_ptrace_hbp_set(NT_ARM_HW_BREAK, tsk, num, &kdata);
-	set_fs(old_fs);
 
 	return ret;
 }