[PATCH -mm 1/1] signal: simplify set_user_sigmask/restore_user_sigmask

From: Oleg Nesterov
Date: Wed Jun 05 2019 - 12:02:53 EST

task->saved_sigmask and ->restore_sigmask are only used in the ret-from-
syscall paths. This means that set_user_sigmask() can save ->blocked in
->saved_sigmask and do set_restore_sigmask() to indicate that ->blocked
was modified.

This way the callers do not need 2 sigset_t's passed to set/restore and
restore_user_sigmask() renamed to restore_saved_sigmask_unless() turns
into the trivial helper which just calls restore_saved_sigmask().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
fs/aio.c | 20 +++++--------
fs/eventpoll.c | 12 +++-----
fs/io_uring.c | 11 ++-----
fs/select.c | 34 ++++++++--------------
include/linux/compat.h | 3 +-
include/linux/sched/signal.h | 12 ++++++--
include/linux/signal.h | 4 ---
kernel/signal.c | 69 ++++++++++++--------------------------------
8 files changed, 57 insertions(+), 108 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index c1e581d..8200f97 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -2093,7 +2093,6 @@ SYSCALL_DEFINE6(io_pgetevents,
const struct __aio_sigset __user *, usig)
{
struct __aio_sigset ksig = { NULL, };
- sigset_t ksigmask, sigsaved;
struct timespec64 ts;
bool interrupted;
int ret;
@@ -2104,14 +2103,14 @@ SYSCALL_DEFINE6(io_pgetevents,
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;

- ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+ ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;

ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);

interrupted = signal_pending(current);
- restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
+ restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;

@@ -2129,7 +2128,6 @@ SYSCALL_DEFINE6(io_pgetevents_time32,
const struct __aio_sigset __user *, usig)
{
struct __aio_sigset ksig = { NULL, };
- sigset_t ksigmask, sigsaved;
struct timespec64 ts;
bool interrupted;
int ret;
@@ -2141,14 +2139,14 @@ SYSCALL_DEFINE6(io_pgetevents_time32,
return -EFAULT;


- ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+ ret = set_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;

ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);

interrupted = signal_pending(current);
- restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
+ restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;

@@ -2197,7 +2195,6 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
const struct __compat_aio_sigset __user *, usig)
{
struct __compat_aio_sigset ksig = { NULL, };
- sigset_t ksigmask, sigsaved;
struct timespec64 t;
bool interrupted;
int ret;
@@ -2208,14 +2205,14 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;

- ret = set_compat_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+ ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;

ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);

interrupted = signal_pending(current);
- restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
+ restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;

@@ -2233,7 +2230,6 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
const struct __compat_aio_sigset __user *, usig)
{
struct __compat_aio_sigset ksig = { NULL, };
- sigset_t ksigmask, sigsaved;
struct timespec64 t;
bool interrupted;
int ret;
@@ -2244,14 +2240,14 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents_time64,
if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
return -EFAULT;

- ret = set_compat_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+ ret = set_compat_user_sigmask(ksig.sigmask, ksig.sigsetsize);
if (ret)
return ret;

ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);

interrupted = signal_pending(current);
- restore_user_sigmask(ksig.sigmask, &sigsaved, interrupted);
+ restore_saved_sigmask_unless(interrupted);
if (interrupted && !ret)
ret = -ERESTARTNOHAND;

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 4c74c76..0f9c073 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2313,19 +2313,17 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
size_t, sigsetsize)
{
int error;
- sigset_t ksigmask, sigsaved;

/*
* If the caller wants a certain signal mask to be set during the wait,
* we apply it here.
*/
- error = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ error = set_user_sigmask(sigmask, sigsetsize);
if (error)
return error;

error = do_epoll_wait(epfd, events, maxevents, timeout);
-
- restore_user_sigmask(sigmask, &sigsaved, error == -EINTR);
+ restore_saved_sigmask_unless(error == -EINTR);

return error;
}
@@ -2338,19 +2336,17 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
compat_size_t, sigsetsize)
{
long err;
- sigset_t ksigmask, sigsaved;

/*
* If the caller wants a certain signal mask to be set during the wait,
* we apply it here.
*/
- err = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ err = set_compat_user_sigmask(sigmask, sigsetsize);
if (err)
return err;

err = do_epoll_wait(epfd, events, maxevents, timeout);
-
- restore_user_sigmask(sigmask, &sigsaved, err == -EINTR);
+ restore_saved_sigmask_unless(err == -EINTR);

return err;
}
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1147c5d..ad7b9bc 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2180,7 +2180,6 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
const sigset_t __user *sig, size_t sigsz)
{
struct io_cq_ring *ring = ctx->cq_ring;
- sigset_t ksigmask, sigsaved;
int ret;

if (io_cqring_events(ring) >= min_events)
@@ -2190,21 +2189,17 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
#ifdef CONFIG_COMPAT
if (in_compat_syscall())
ret = set_compat_user_sigmask((const compat_sigset_t __user *)sig,
- &ksigmask, &sigsaved, sigsz);
+ sigsz);
else
#endif
- ret = set_user_sigmask(sig, &ksigmask,
- &sigsaved, sigsz);
+ ret = set_user_sigmask(sig, sigsz);

if (ret)
return ret;
}

ret = wait_event_interruptible(ctx->wait, io_cqring_events(ring) >= min_events);
-
- if (sig)
- restore_user_sigmask(sig, &sigsaved, ret == -ERESTARTSYS);
-
+ restore_saved_sigmask_unless(ret == -ERESTARTSYS);
if (ret == -ERESTARTSYS)
ret = -EINTR;

diff --git a/fs/select.c b/fs/select.c
index a4d8f6e..1fc1b24 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -730,7 +730,6 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
const sigset_t __user *sigmask, size_t sigsetsize,
enum poll_time_type type)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -753,12 +752,12 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
return -EINVAL;
}

- ret = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = core_sys_select(n, inp, outp, exp, to);
- restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);
+ restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
ret = poll_select_copy_remaining(&end_time, tsp, type, ret);

return ret;
@@ -1086,7 +1085,6 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
struct __kernel_timespec __user *, tsp, const sigset_t __user *, sigmask,
size_t, sigsetsize)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -1099,17 +1097,16 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
return -EINVAL;
}

- ret = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = do_sys_poll(ufds, nfds, to);

- restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
+ restore_saved_sigmask_unless(ret == -EINTR);
/* We can restart this syscall, usually */
if (ret == -EINTR)
ret = -ERESTARTNOHAND;
-
ret = poll_select_copy_remaining(&end_time, tsp, PT_TIMESPEC, ret);

return ret;
@@ -1121,7 +1118,6 @@ SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds,
struct old_timespec32 __user *, tsp, const sigset_t __user *, sigmask,
size_t, sigsetsize)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -1134,17 +1130,16 @@ SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds,
return -EINVAL;
}

- ret = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = do_sys_poll(ufds, nfds, to);

- restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
+ restore_saved_sigmask_unless(ret == -EINTR);
/* We can restart this syscall, usually */
if (ret == -EINTR)
ret = -ERESTARTNOHAND;
-
ret = poll_select_copy_remaining(&end_time, tsp, PT_OLD_TIMESPEC, ret);

return ret;
@@ -1319,7 +1314,6 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
void __user *tsp, compat_sigset_t __user *sigmask,
compat_size_t sigsetsize, enum poll_time_type type)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -1342,12 +1336,12 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
return -EINVAL;
}

- ret = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_compat_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = compat_core_sys_select(n, inp, outp, exp, to);
- restore_user_sigmask(sigmask, &sigsaved, ret == -ERESTARTNOHAND);
+ restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
ret = poll_select_copy_remaining(&end_time, tsp, type, ret);

return ret;
@@ -1402,7 +1396,6 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds,
unsigned int, nfds, struct old_timespec32 __user *, tsp,
const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -1415,17 +1408,16 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds,
return -EINVAL;
}

- ret = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_compat_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = do_sys_poll(ufds, nfds, to);

- restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
+ restore_saved_sigmask_unless(ret == -EINTR);
/* We can restart this syscall, usually */
if (ret == -EINTR)
ret = -ERESTARTNOHAND;
-
ret = poll_select_copy_remaining(&end_time, tsp, PT_OLD_TIMESPEC, ret);

return ret;
@@ -1437,7 +1429,6 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds,
unsigned int, nfds, struct __kernel_timespec __user *, tsp,
const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
{
- sigset_t ksigmask, sigsaved;
struct timespec64 ts, end_time, *to = NULL;
int ret;

@@ -1450,17 +1441,16 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds,
return -EINVAL;
}

- ret = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+ ret = set_compat_user_sigmask(sigmask, sigsetsize);
if (ret)
return ret;

ret = do_sys_poll(ufds, nfds, to);

- restore_user_sigmask(sigmask, &sigsaved, ret == -EINTR);
+ restore_saved_sigmask_unless(ret == -EINTR);
/* We can restart this syscall, usually */
if (ret == -EINTR)
ret = -ERESTARTNOHAND;
-
ret = poll_select_copy_remaining(&end_time, tsp, PT_TIMESPEC, ret);

return ret;
diff --git a/include/linux/compat.h b/include/linux/compat.h
index ebddcb6..16dafd9 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -138,8 +138,7 @@ typedef struct {
compat_sigset_word sig[_COMPAT_NSIG_WORDS];
} compat_sigset_t;

-int set_compat_user_sigmask(const compat_sigset_t __user *usigmask,
- sigset_t *set, sigset_t *oldset,
+int set_compat_user_sigmask(const compat_sigset_t __user *umask,
size_t sigsetsize);

struct compat_sigaction {
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 38a0f07..4d9c71d 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -417,7 +417,6 @@ void task_join_group_stop(struct task_struct *task);
static inline void set_restore_sigmask(void)
{
set_thread_flag(TIF_RESTORE_SIGMASK);
- WARN_ON(!test_thread_flag(TIF_SIGPENDING));
}

static inline void clear_tsk_restore_sigmask(struct task_struct *task)
@@ -448,7 +447,6 @@ static inline bool test_and_clear_restore_sigmask(void)
static inline void set_restore_sigmask(void)
{
current->restore_sigmask = true;
- WARN_ON(!test_thread_flag(TIF_SIGPENDING));
}
static inline void clear_tsk_restore_sigmask(struct task_struct *task)
{
@@ -481,6 +479,16 @@ static inline void restore_saved_sigmask(void)
__set_current_blocked(&current->saved_sigmask);
}

+extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);
+
+static inline void restore_saved_sigmask_unless(bool interrupted)
+{
+ if (interrupted)
+ WARN_ON(!test_thread_flag(TIF_SIGPENDING));
+ else
+ restore_saved_sigmask();
+}
+
static inline sigset_t *sigmask_to_save(void)
{
sigset_t *res = &current->blocked;
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 78c2bb3..b5d99482 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -273,10 +273,6 @@ extern int group_send_sig_info(int sig, struct kernel_siginfo *info,
struct task_struct *p, enum pid_type type);
extern int __group_send_sig_info(int, struct kernel_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, bool interrupted);
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 aa6a6f1..51772da 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2863,80 +2863,49 @@ EXPORT_SYMBOL(sigprocmask);
*
* This is useful for syscalls such as ppoll, pselect, io_pgetevents and
* epoll_pwait where a new sigmask is passed from userland for the syscalls.
+ *
+ * Note that it does set_restore_sigmask() in advance, so it must be always
+ * paired with restore_saved_sigmask_unless() before return from syscall.
*/
-int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,
- sigset_t *oldset, size_t sigsetsize)
+int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize)
{
- if (!usigmask)
- return 0;
+ sigset_t *kmask;

+ if (!umask)
+ return 0;
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
- if (copy_from_user(set, usigmask, sizeof(sigset_t)))
+ if (copy_from_user(kmask, umask, sizeof(sigset_t)))
return -EFAULT;

- *oldset = current->blocked;
- set_current_blocked(set);
+ set_restore_sigmask();
+ current->saved_sigmask = current->blocked;
+ set_current_blocked(kmask);

return 0;
}
-EXPORT_SYMBOL(set_user_sigmask);

#ifdef CONFIG_COMPAT
-int set_compat_user_sigmask(const compat_sigset_t __user *usigmask,
- sigset_t *set, sigset_t *oldset,
+int set_compat_user_sigmask(const compat_sigset_t __user *umask,
size_t sigsetsize)
{
- if (!usigmask)
- return 0;
+ sigset_t *kmask;

+ if (!umask)
+ return 0;
if (sigsetsize != sizeof(compat_sigset_t))
return -EINVAL;
- if (get_compat_sigset(set, usigmask))
+ if (get_compat_sigset(kmask, umask))
return -EFAULT;

- *oldset = current->blocked;
- set_current_blocked(set);
+ set_restore_sigmask();
+ current->saved_sigmask = current->blocked;
+ set_current_blocked(kmask);

return 0;
}
-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,
- bool interrupted)
-{
-
- 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 (interrupted) {
- 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
--
2.5.0