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Message-Id: <20180901204721.13117-3-deepa.kernel@gmail.com>
Date: Sat, 1 Sep 2018 13:47:18 -0700
From: Deepa Dinamani <deepa.kernel@...il.com>
To: viro@...iv.linux.org.uk, tglx@...utronix.de,
linux-kernel@...r.kernel.org
Cc: arnd@...db.de, y2038@...ts.linaro.org,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
linux-aio@...ck.org
Subject: [PATCH 2/5] signal: Add restore_user_sigmask()
Refactor the logic to restore the sigmask before the syscall
returns into an api.
This is useful for versions of syscalls that pass in the
sigmask and expect the current->sigmask to be changed during
the execution and restored after the execution of the syscall.
With the advent of new y2038 syscalls in the subsequent patches,
we add 2 more new versions of the syscalls(for pselect, ppoll
and io_pgetevents) in addition to the existing native and compat
versions. Adding such an api reduces the logic that would need to
be replicated otherwise.
Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
---
fs/aio.c | 29 +++++---------------
fs/eventpoll.c | 30 ++-------------------
fs/select.c | 60 ++++++------------------------------------
include/linux/signal.h | 2 ++
kernel/signal.c | 33 +++++++++++++++++++++++
5 files changed, 51 insertions(+), 103 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 67e5b1f6fb0f..b81c216534d6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -2111,18 +2111,9 @@ SYSCALL_DEFINE6(io_pgetevents,
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
- if (signal_pending(current)) {
- if (ksig.sigmask) {
- current->saved_sigmask = sigsaved;
- set_restore_sigmask();
- }
-
- if (!ret)
- ret = -ERESTARTNOHAND;
- } else {
- if (ksig.sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
- }
+ restore_user_sigmask(ksig.sigmask, &sigsaved);
+ if (signal_pending(current) && !ret)
+ ret = -ERESTARTNOHAND;
return ret;
}
@@ -2176,17 +2167,9 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
return ret;
ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
- if (signal_pending(current)) {
- if (ksig.sigmask) {
- current->saved_sigmask = sigsaved;
- set_restore_sigmask();
- }
- if (!ret)
- ret = -ERESTARTNOHAND;
- } else {
- if (ksig.sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
- }
+ restore_user_sigmask(ksig.sigmask, &sigsaved);
+ if (signal_pending(current) && !ret)
+ ret = -ERESTARTNOHAND;
return ret;
}
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 2d86eeba837b..8a5a1010886b 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2229,20 +2229,7 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
error = do_epoll_wait(epfd, events, maxevents, timeout);
- /*
- * If we changed the signal mask, we need to restore the original one.
- * In case we've got a signal while waiting, we do not restore the
- * signal mask yet, and we allow do_signal() to deliver the signal on
- * the way back to userspace, before the signal mask is restored.
- */
- if (sigmask) {
- if (error == -EINTR) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- } else
- set_current_blocked(&sigsaved);
- }
+ restore_user_sigmask(sigmask, &sigsaved);
return error;
}
@@ -2267,20 +2254,7 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
err = do_epoll_wait(epfd, events, maxevents, timeout);
- /*
- * If we changed the signal mask, we need to restore the original one.
- * In case we've got a signal while waiting, we do not restore the
- * signal mask yet, and we allow do_signal() to deliver the signal on
- * the way back to userspace, before the signal mask is restored.
- */
- if (sigmask) {
- if (err == -EINTR) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- } else
- set_current_blocked(&sigsaved);
- }
+ restore_user_sigmask(sigmask, &sigsaved);
return err;
}
diff --git a/fs/select.c b/fs/select.c
index 65c78b4147a2..eb9132520197 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -724,19 +724,7 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
ret = core_sys_select(n, inp, outp, exp, to);
ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
- if (ret == -ERESTARTNOHAND) {
- /*
- * Don't restore the signal mask yet. Let do_signal() deliver
- * the signal on the way back to userspace, before the signal
- * mask is restored.
- */
- if (sigmask) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- }
- } else if (sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+ restore_user_sigmask(sigmask, &sigsaved);
return ret;
}
@@ -1060,21 +1048,11 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
ret = do_sys_poll(ufds, nfds, to);
+ restore_user_sigmask(sigmask, &sigsaved);
+
/* We can restart this syscall, usually */
- if (ret == -EINTR) {
- /*
- * Don't restore the signal mask yet. Let do_signal() deliver
- * the signal on the way back to userspace, before the signal
- * mask is restored.
- */
- if (sigmask) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- }
+ if (ret == -EINTR)
ret = -ERESTARTNOHAND;
- } else if (sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
@@ -1316,19 +1294,7 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
ret = compat_core_sys_select(n, inp, outp, exp, to);
ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
- if (ret == -ERESTARTNOHAND) {
- /*
- * Don't restore the signal mask yet. Let do_signal() deliver
- * the signal on the way back to userspace, before the signal
- * mask is restored.
- */
- if (sigmask) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- }
- } else if (sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+ restore_user_sigmask(sigmask, &sigsaved);
return ret;
}
@@ -1375,21 +1341,11 @@ COMPAT_SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds,
ret = do_sys_poll(ufds, nfds, to);
+ restore_user_sigmask(sigmask, &sigsaved);
+
/* We can restart this syscall, usually */
- if (ret == -EINTR) {
- /*
- * Don't restore the signal mask yet. Let do_signal() deliver
- * the signal on the way back to userspace, before the signal
- * mask is restored.
- */
- if (sigmask) {
- memcpy(¤t->saved_sigmask, &sigsaved,
- sizeof(sigsaved));
- set_restore_sigmask();
- }
+ if (ret == -EINTR)
ret = -ERESTARTNOHAND;
- } else if (sigmask)
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 403e63d01bcf..ed8be17afe89 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -265,6 +265,8 @@ extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
extern int sigprocmask(int, sigset_t *, sigset_t *);
extern int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,
sigset_t *oldset, size_t sigsetsize);
+extern void restore_user_sigmask(const void __user *usigmask,
+ sigset_t *sigsaved);
extern void set_current_blocked(sigset_t *);
extern void __set_current_blocked(const sigset_t *);
extern int show_unhandled_signals;
diff --git a/kernel/signal.c b/kernel/signal.c
index 1d72dcddcaaf..457d1abe62a4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2783,6 +2783,39 @@ int set_compat_user_sigmask(const compat_sigset_t __user *usigmask,
EXPORT_SYMBOL(set_compat_user_sigmask);
#endif
+/*
+ * restore_user_sigmask:
+ * usigmask: sigmask passed in from userland.
+ * sigsaved: saved sigmask when the syscall started and changed the sigmask to
+ * usigmask.
+ *
+ * This is useful for syscalls such as ppoll, pselect, io_pgetevents and
+ * epoll_pwait where a new sigmask is passed in from userland for the syscalls.
+ */
+void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
+{
+
+ if (!usigmask)
+ return;
+ /*
+ * When signals are pending, do not restore them here.
+ * Restoring sigmask here can lead to delivering signals that the above
+ * syscalls are intended to block because of the sigmask passed in.
+ */
+ if (signal_pending(current)) {
+ current->saved_sigmask = *sigsaved;
+ set_restore_sigmask();
+ return;
+ }
+
+ /*
+ * This is needed because the fast syscall return path does not restore
+ * saved_sigmask when signals are not pending.
+ */
+ set_current_blocked(sigsaved);
+}
+EXPORT_SYMBOL(restore_user_sigmask);
+
/**
* sys_rt_sigprocmask - change the list of currently blocked signals
* @how: whether to add, remove, or set signals
--
2.17.1
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