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Subject[PATCH 3/4] signal/x86: Move nosig handling at the end of exit_to_usermode_loop.
Date
Handling of restarting a system call for nosig should be done after
all possible calls of do_signal, to see if it's actually delivering
signal(s) or not.

Before this change, restarting a system call for nosig may be followed
by a call of handle_signal which would try to change the system call
returning -EINTR instead, but it is too late to do so.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
---
arch/x86/entry/common.c | 6 +++++-
arch/x86/include/asm/signal.h | 2 +-
arch/x86/kernel/signal.c | 6 +++---
3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 74f6eee15179..38e0939c0aeb 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -137,6 +137,8 @@ static long syscall_trace_enter(struct pt_regs *regs)

static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
{
+ int nosig = 0;
+
/*
* In order to return to user mode, we need to have IRQs off with
* none of EXIT_TO_USERMODE_LOOP_FLAGS set. Several of these flags
@@ -159,7 +161,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)

/* deal with pending signal delivery */
if (cached_flags & _TIF_SIGPENDING)
- do_signal(regs);
+ nosig |= do_signal(regs);

if (cached_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
@@ -177,6 +179,8 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
break;
}
+ if (nosig)
+ nosig_restart_syscall(regs);
}

/* Called with IRQs disabled. */
diff --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h
index 6517df6d9938..31e68266c2f6 100644
--- a/arch/x86/include/asm/signal.h
+++ b/arch/x86/include/asm/signal.h
@@ -35,7 +35,7 @@ typedef sigset_t compat_sigset_t;
#endif /* __ASSEMBLY__ */
#include <uapi/asm/signal.h>
#ifndef __ASSEMBLY__
-extern void do_signal(struct pt_regs *regs);
+extern int do_signal(struct pt_regs *regs);
extern void nosig_restart_syscall(struct pt_regs *regs);

#define __ARCH_HAS_SA_RESTORER
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index e709b54a01b8..57576988a01f 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -803,17 +803,17 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
-void do_signal(struct pt_regs *regs)
+int do_signal(struct pt_regs *regs)
{
struct ksignal ksig;

if (get_signal(&ksig)) {
/* Whee! Actually deliver the signal. */
handle_signal(&ksig, regs);
- return;
+ return 0;
}

- nosig_restart_syscall(regs);
+ return 1;
}

void nosig_restart_syscall(struct pt_regs *regs)
--
2.11.0
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