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Subject[PATCH 3.12 18/66] uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME
Date
From: Andy Lutomirski <luto@amacapital.net>

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

===============

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@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
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 27811190cbd7..bbbac9207419 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -145,7 +145,7 @@ 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 ad8e1bdca70e..8176caf6efd9 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1511,7 +1511,6 @@ 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);
}
}

--
2.1.3


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