linux-kernel - [PATCH 3.17 018/122] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY

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Date:	Fri,  5 Dec 2014 14:43:12 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.17 018/122] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME

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

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

From: Andy Lutomirski <luto@...capital.net>

commit 82975bc6a6df743b9a01810fb32cb65d0ec5d60b upstream.

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.

Reported-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Acked-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Andy Lutomirski <luto@...capital.net>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/thread_info.h |    2 +-
 kernel/events/uprobes.c            |    1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

--- 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							\
--- 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);
 		}
 	}
 


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