linux-kernel - [PATCH v2 2/2] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY

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Date:	Thu, 13 Nov 2014 14:31:21 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>, x86@...nel.org
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andy Lutomirski <luto@...capital.net>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: [PATCH v2 2/2] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME

x86 call do_notify_resume on paranoid returns if TIF_UPROBE is set
but not on non-paranoid returns.  I suspect that this is a mistake
and that the code only works because int3 is paranoid.

Setting _TIF_NOTIFY_RESUME in the uprobe code was probably a
workaround for the x86 bug.  With that bug fixed, we can remove
_TIF_NOTIFY_RESUME from the uprobes code.

Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Reported-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 arch/x86/include/asm/thread_info.h | 2 +-
 kernel/events/uprobes.c            | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 854053889d4d..547e344a6dc6 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -141,7 +141,7 @@ struct thread_info {
 /* Only used for 64 bit */
 #define _TIF_DO_NOTIFY_MASK						\
 	(_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME |	\
-	 _TIF_USER_RETURN_NOTIFY)
+	 _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE)
 
 /* flags to check in __switch_to() */
 #define _TIF_WORK_CTXSW							\
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 1d0af8a2c646..ed8f2cde34c5 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1640,7 +1640,6 @@ bool uprobe_deny_signal(void)
 		if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
 			utask->state = UTASK_SSTEP_TRAPPED;
 			set_tsk_thread_flag(t, TIF_UPROBE);
-			set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
 		}
 	}
 
-- 
1.9.3

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