linux-kernel - [PATCH 02/13] ptrace/powerpc: Revert "hw_breakpoints: Fix racy access to ptrace breakpoints"

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Message-ID: <20130513151702.GA6246@redhat.com>
Date:	Mon, 13 May 2013 17:17:02 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	Michael Neuling <mikey@...ling.org>,
	Paul Mackerras <paulus@...ba.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Prasad <prasad@...ux.vnet.ibm.com>,
	Russell King <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 02/13] ptrace/powerpc: Revert "hw_breakpoints: Fix racy
	access to ptrace breakpoints"

This reverts commit 07fa7a0a8a586c01a8b416358c7012dcb9dc688d and
removes ptrace_get/put_breakpoints() added by other commits.

The patch was fine but we can no longer race with SIGKILL after
9899d11f "ptrace: ensure arch_ptrace/ptrace_request can never race
with SIGKILL", the __TASK_TRACED tracee can't be woken up and
->ptrace_bps[] can't go away.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Michael Neuling <mikey@...ling.org>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
---
 arch/powerpc/kernel/ptrace.c |   20 --------------------
 1 files changed, 0 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 3b14d32..0f28c19 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -974,16 +974,12 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 	hw_brk.type = (data & HW_BRK_TYPE_DABR) | HW_BRK_TYPE_PRIV_ALL;
 	hw_brk.len = 8;
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-	if (ptrace_get_breakpoints(task) < 0)
-		return -ESRCH;
-
 	bp = thread->ptrace_bps[0];
 	if ((!data) || !(hw_brk.type & HW_BRK_TYPE_RDWR)) {
 		if (bp) {
 			unregister_hw_breakpoint(bp);
 			thread->ptrace_bps[0] = NULL;
 		}
-		ptrace_put_breakpoints(task);
 		return 0;
 	}
 	if (bp) {
@@ -996,11 +992,9 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 
 		ret =  modify_user_hw_breakpoint(bp, &attr);
 		if (ret) {
-			ptrace_put_breakpoints(task);
 			return ret;
 		}
 		thread->ptrace_bps[0] = bp;
-		ptrace_put_breakpoints(task);
 		thread->hw_brk = hw_brk;
 		return 0;
 	}
@@ -1015,12 +1009,9 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
 					       ptrace_triggered, NULL, task);
 	if (IS_ERR(bp)) {
 		thread->ptrace_bps[0] = NULL;
-		ptrace_put_breakpoints(task);
 		return PTR_ERR(bp);
 	}
 
-	ptrace_put_breakpoints(task);
-
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
 	task->thread.hw_brk = hw_brk;
 #else /* CONFIG_PPC_ADV_DEBUG_REGS */
@@ -1439,9 +1430,6 @@ static long ppc_set_hwdebug(struct task_struct *child,
 	if (bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_WRITE)
 		brk.type |= HW_BRK_TYPE_WRITE;
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-	if (ptrace_get_breakpoints(child) < 0)
-		return -ESRCH;
-
 	/*
 	 * Check if the request is for 'range' breakpoints. We can
 	 * support it if range < 8 bytes.
@@ -1449,12 +1437,10 @@ static long ppc_set_hwdebug(struct task_struct *child,
 	if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE) {
 		len = bp_info->addr2 - bp_info->addr;
 	} else if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT) {
-		ptrace_put_breakpoints(child);
 		return -EINVAL;
 	}
 	bp = thread->ptrace_bps[0];
 	if (bp) {
-		ptrace_put_breakpoints(child);
 		return -ENOSPC;
 	}
 
@@ -1468,11 +1454,9 @@ static long ppc_set_hwdebug(struct task_struct *child,
 					       ptrace_triggered, NULL, child);
 	if (IS_ERR(bp)) {
 		thread->ptrace_bps[0] = NULL;
-		ptrace_put_breakpoints(child);
 		return PTR_ERR(bp);
 	}
 
-	ptrace_put_breakpoints(child);
 	return 1;
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
 
@@ -1516,16 +1500,12 @@ static long ppc_del_hwdebug(struct task_struct *child, long data)
 		return -EINVAL;
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-	if (ptrace_get_breakpoints(child) < 0)
-		return -ESRCH;
-
 	bp = thread->ptrace_bps[0];
 	if (bp) {
 		unregister_hw_breakpoint(bp);
 		thread->ptrace_bps[0] = NULL;
 	} else
 		ret = -ENOENT;
-	ptrace_put_breakpoints(child);
 	return ret;
 #else /* CONFIG_HAVE_HW_BREAKPOINT */
 	if (child->thread.hw_brk.address == 0)
-- 
1.5.5.1

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