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>

diff --git a/fs/aio.c b/fs/aio.c
index 301e6314183b66756077fed9e37630cc5436ff40..6ddb63ee8eb61ced737e9586833ad666767db4e6 100644 (file)
--- 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 42bbe6824b4bffc1fb5388c993abf102fcd8ea2b..2d86eeba837b958fe7cb8705aea6d45a9ca31bb0 100644 (file)
--- 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 22b3bf89f051e9c60bd96ce4ce24024f6b5e84d6..65c78b4147a2ab4958196aaf901e4ba5ca6b6494 100644 (file)
--- 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);
 

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 88720b443cd646f588fa183d60a0f5c549fc030e..17c497b826901f7daf0952bf80fd69e4c16090f5 100644 (file)
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -169,6 +169,10 @@ 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,
+                           size_t sigsetsize);
+
 struct compat_sigaction {
 #ifndef __ARCH_HAS_IRIX_SIGACTION
        compat_uptr_t                   sa_handler;

diff --git a/include/linux/signal.h b/include/linux/signal.h
index f428e86f480075fe0c2a8a71938616fdd6ee8dcc..ce14b951befb8b1080e1a228a957a437a1279b36 100644 (file)
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -273,6 +273,8 @@ 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 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 9a32bc2088c90c709cc2acc336f0ac3d68342931..811b5d4406179900fecaace5b00f4bcd819fe98f 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2735,6 +2735,51 @@ int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
 }
 EXPORT_SYMBOL(sigprocmask);
 
+/*
+ * The api helps set app-provided sigmasks.
+ *
+ * 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.
+ */
+int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set,
+                    sigset_t *oldset, size_t sigsetsize)
+{
+       if (!usigmask)
+               return 0;
+
+       if (sigsetsize != sizeof(sigset_t))
+               return -EINVAL;
+       if (copy_from_user(set, usigmask, sizeof(sigset_t)))
+               return -EFAULT;
+
+       *oldset = current->blocked;
+       set_current_blocked(set);
+
+       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,
+                           size_t sigsetsize)
+{
+       if (!usigmask)
+               return 0;
+
+       if (sigsetsize != sizeof(compat_sigset_t))
+               return -EINVAL;
+       if (get_compat_sigset(set, usigmask))
+               return -EFAULT;
+
+       *oldset = current->blocked;
+       set_current_blocked(set);
+
+       return 0;
+}
+EXPORT_SYMBOL(set_compat_user_sigmask);
+#endif
+
 /**
  *  sys_rt_sigprocmask - change the list of currently blocked signals
  *  @how: whether to add, remove, or set signals