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    Subject[PATCH -mm 1/1] signal: simplify set_user_sigmask/restore_user_sigmask
    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@redhat.com>
    ---
    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

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