signal: Add set_user_sigmask()

Refactor reading sigset from userspace and updating sigmask
into an api.

This is useful for versions of syscalls that pass in the
sigmask and expect the current->sigmask to be changed during,
and restored after, the execution of the syscall.

With the advent of new y2038 syscalls in the subsequent patches,
we add two 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.

Note that the calls to sigprocmask() ignored the return value
from the api as the function only returns an error on an invalid
first argument that is hardcoded at these call sites.
The updated logic uses set_current_blocked() instead.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

3 files changed, 25 insertions, 70 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 301e6314183b..6ddb63ee8eb6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -2104,14 +2104,10 @@ SYSCALL_DEFINE6(io_pgetevents,
 	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
 		return -EFAULT;
 
-	if (ksig.sigmask) {
-		if (ksig.sigsetsize != sizeof(sigset_t))
-			return -EINVAL;
-		if (copy_from_user(&ksigmask, ksig.sigmask, sizeof(ksigmask)))
-			return -EFAULT;
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+
+	ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
 	if (signal_pending(current)) {
@@ -2174,14 +2170,9 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
 	if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
 		return -EFAULT;
 
-	if (ksig.sigmask) {
-		if (ksig.sigsetsize != sizeof(compat_sigset_t))
-			return -EINVAL;
-		if (get_compat_sigset(&ksigmask, ksig.sigmask))
-			return -EFAULT;
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+	ret = set_compat_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
 	if (signal_pending(current)) {
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 42bbe6824b4b..2d86eeba837b 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2223,14 +2223,9 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
 	 * If the caller wants a certain signal mask to be set during the wait,
 	 * we apply it here.
 	 */
-	if (sigmask) {
-		if (sigsetsize != sizeof(sigset_t))
-			return -EINVAL;
-		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
-			return -EFAULT;
-		sigsaved = current->blocked;
-		set_current_blocked(&ksigmask);
-	}
+	error = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (error)
+		return error;
 
 	error = do_epoll_wait(epfd, events, maxevents, timeout);
 
@@ -2266,14 +2261,9 @@ COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
 	 * If the caller wants a certain signal mask to be set during the wait,
 	 * we apply it here.
 	 */
-	if (sigmask) {
-		if (sigsetsize != sizeof(compat_sigset_t))
-			return -EINVAL;
-		if (get_compat_sigset(&ksigmask, sigmask))
-			return -EFAULT;
-		sigsaved = current->blocked;
-		set_current_blocked(&ksigmask);
-	}
+	err = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (err)
+		return err;
 
 	err = do_epoll_wait(epfd, events, maxevents, timeout);
 
diff --git a/fs/select.c b/fs/select.c
index 22b3bf89f051..65c78b4147a2 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -717,16 +717,9 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
 			return -EINVAL;
 	}
 
-	if (sigmask) {
-		/* XXX: Don't preclude handling different sized sigset_t's.  */
-		if (sigsetsize != sizeof(sigset_t))
-			return -EINVAL;
-		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
-			return -EFAULT;
-
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+	ret = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = core_sys_select(n, inp, outp, exp, to);
 	ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
@@ -1061,16 +1054,9 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
 			return -EINVAL;
 	}
 
-	if (sigmask) {
-		/* XXX: Don't preclude handling different sized sigset_t's.  */
-		if (sigsetsize != sizeof(sigset_t))
-			return -EINVAL;
-		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
-			return -EFAULT;
-
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+	ret = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
 
@@ -1323,15 +1309,9 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
 			return -EINVAL;
 	}
 
-	if (sigmask) {
-		if (sigsetsize != sizeof(compat_sigset_t))
-			return -EINVAL;
-		if (get_compat_sigset(&ksigmask, sigmask))
-			return -EFAULT;
-
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+	ret = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = compat_core_sys_select(n, inp, outp, exp, to);
 	ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
@@ -1389,15 +1369,9 @@ COMPAT_SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds,
 			return -EINVAL;
 	}
 
-	if (sigmask) {
-		if (sigsetsize != sizeof(compat_sigset_t))
-			return -EINVAL;
-		if (get_compat_sigset(&ksigmask, sigmask))
-			return -EFAULT;
-
-		sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
-		sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
-	}
+	ret = set_compat_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
+	if (ret)
+		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);