waitid(2): leave copyout of siginfo to syscall itself

have kernel_waitid() collect the information needed for siginfo into
a small structure (waitid_info) passed to it; deal with copyout in
sys_waitid()/compat_sys_waitid().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/kernel/exit.c b/kernel/exit.c
index 94cdccf8e7e758e97bdd6bf320152b49ab957d5d..42f26480b3cccd297bdc971e39d6efff67e9e15c 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -996,12 +996,19 @@ SYSCALL_DEFINE1(exit_group, int, error_code)
        return 0;
 }
 
+struct waitid_info {
+       pid_t pid;
+       uid_t uid;
+       int status;
+       int cause;
+};
+
 struct wait_opts {
        enum pid_type           wo_type;
        int                     wo_flags;
        struct pid              *wo_pid;
 
-       struct siginfo __user   *wo_info;
+       struct waitid_info      *wo_info;
        int                     wo_stat;
        struct rusage           *wo_rusage;
 
@@ -1053,8 +1060,7 @@ eligible_child(struct wait_opts *wo, bool ptrace, struct task_struct *p)
 static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
                                pid_t pid, uid_t uid, int why, int status)
 {
-       struct siginfo __user *infop;
-       int retval = 0;
+       struct waitid_info *infop;
 
        if (wo->wo_rusage)
                getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
@@ -1062,22 +1068,12 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
        put_task_struct(p);
        infop = wo->wo_info;
        if (infop) {
-               if (!retval)
-                       retval = put_user(SIGCHLD, &infop->si_signo);
-               if (!retval)
-                       retval = put_user(0, &infop->si_errno);
-               if (!retval)
-                       retval = put_user((short)why, &infop->si_code);
-               if (!retval)
-                       retval = put_user(pid, &infop->si_pid);
-               if (!retval)
-                       retval = put_user(uid, &infop->si_uid);
-               if (!retval)
-                       retval = put_user(status, &infop->si_status);
+               infop->cause = why;
+               infop->pid = pid;
+               infop->uid = uid;
+               infop->status = status;
        }
-       if (!retval)
-               retval = pid;
-       return retval;
+       return pid;
 }
 
 /*
@@ -1088,10 +1084,10 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
  */
 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 {
-       int state, retval, status;
+       int state, status;
        pid_t pid = task_pid_vnr(p);
        uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
-       struct siginfo __user *infop;
+       struct waitid_info *infop;
 
        if (!likely(wo->wo_flags & WEXITED))
                return 0;
@@ -1186,36 +1182,22 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 
        if (wo->wo_rusage)
                getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
-       retval = 0;
        status = (p->signal->flags & SIGNAL_GROUP_EXIT)
                ? p->signal->group_exit_code : p->exit_code;
        wo->wo_stat = status;
 
        infop = wo->wo_info;
-       if (!retval && infop)
-               retval = put_user(SIGCHLD, &infop->si_signo);
-       if (!retval && infop)
-               retval = put_user(0, &infop->si_errno);
-       if (!retval && infop) {
-               int why;
-
+       if (infop) {
                if ((status & 0x7f) == 0) {
-                       why = CLD_EXITED;
-                       status >>= 8;
+                       infop->cause = CLD_EXITED;
+                       infop->status = status >> 8;
                } else {
-                       why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
-                       status &= 0x7f;
+                       infop->cause = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
+                       infop->status = status & 0x7f;
                }
-               retval = put_user((short)why, &infop->si_code);
-               if (!retval)
-                       retval = put_user(status, &infop->si_status);
+               infop->pid = pid;
+               infop->uid = uid;
        }
-       if (!retval && infop)
-               retval = put_user(pid, &infop->si_pid);
-       if (!retval && infop)
-               retval = put_user(uid, &infop->si_uid);
-       if (!retval)
-               retval = pid;
 
        if (state == EXIT_TRACE) {
                write_lock_irq(&tasklist_lock);
@@ -1232,7 +1214,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
        if (state == EXIT_DEAD)
                release_task(p);
 
-       return retval;
+       return pid;
 }
 
 static int *task_stopped_code(struct task_struct *p, bool ptrace)
@@ -1268,8 +1250,8 @@ static int *task_stopped_code(struct task_struct *p, bool ptrace)
 static int wait_task_stopped(struct wait_opts *wo,
                                int ptrace, struct task_struct *p)
 {
-       struct siginfo __user *infop;
-       int retval, exit_code, *p_code, why;
+       struct waitid_info *infop;
+       int exit_code, *p_code, why;
        uid_t uid = 0; /* unneeded, required by compiler */
        pid_t pid;
 
@@ -1320,28 +1302,19 @@ unlock_sig:
 
        if (wo->wo_rusage)
                getrusage(p, RUSAGE_BOTH, wo->wo_rusage);
-       retval = 0;
        wo->wo_stat = (exit_code << 8) | 0x7f;
 
        infop = wo->wo_info;
-       if (!retval && infop)
-               retval = put_user(SIGCHLD, &infop->si_signo);
-       if (!retval && infop)
-               retval = put_user(0, &infop->si_errno);
-       if (!retval && infop)
-               retval = put_user((short)why, &infop->si_code);
-       if (!retval && infop)
-               retval = put_user(exit_code, &infop->si_status);
-       if (!retval && infop)
-               retval = put_user(pid, &infop->si_pid);
-       if (!retval && infop)
-               retval = put_user(uid, &infop->si_uid);
-       if (!retval)
-               retval = pid;
+       if (infop) {
+               infop->cause = why;
+               infop->status = exit_code;
+               infop->pid = pid;
+               infop->uid = uid;
+       }
        put_task_struct(p);
 
-       BUG_ON(!retval);
-       return retval;
+       BUG_ON(!pid);
+       return pid;
 }
 
 /*
@@ -1618,7 +1591,7 @@ end:
        return retval;
 }
 
-static long kernel_waitid(int which, pid_t upid, struct siginfo __user *infop,
+static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
                          int options, struct rusage *ru)
 {
        struct wait_opts wo;
@@ -1660,27 +1633,8 @@ static long kernel_waitid(int which, pid_t upid, struct siginfo __user *infop,
        wo.wo_rusage    = ru;
        ret = do_wait(&wo);
 
-       if (ret > 0) {
+       if (ret > 0)
                ret = 0;
-       } else if (infop) {
-               /*
-                * For a WNOHANG return, clear out all the fields
-                * we would set so the user can easily tell the
-                * difference.
-                */
-               if (!ret)
-                       ret = put_user(0, &infop->si_signo);
-               if (!ret)
-                       ret = put_user(0, &infop->si_errno);
-               if (!ret)
-                       ret = put_user(0, &infop->si_code);
-               if (!ret)
-                       ret = put_user(0, &infop->si_pid);
-               if (!ret)
-                       ret = put_user(0, &infop->si_uid);
-               if (!ret)
-                       ret = put_user(0, &infop->si_status);
-       }
 
        put_pid(pid);
        return ret;
@@ -1690,12 +1644,24 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
                infop, int, options, struct rusage __user *, ru)
 {
        struct rusage r;
-       long err = kernel_waitid(which, upid, infop, options, ru ? &r : NULL);
+       struct waitid_info info = {.status = 0};
+       long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
 
        if (!err) {
                if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
                        return -EFAULT;
        }
+       if (!infop)
+               return err;
+
+       if (put_user(err ? 0 : SIGCHLD, &infop->si_signo) ||
+           put_user(0, &infop->si_errno) ||
+           put_user((short)info.cause, &infop->si_code) ||
+           put_user(info.pid, &infop->si_pid) ||
+           put_user(info.uid, &infop->si_uid) ||
+           put_user(info.status, &infop->si_status))
+               err = -EFAULT;
+
        return err;
 }
 
@@ -1785,33 +1751,27 @@ COMPAT_SYSCALL_DEFINE5(waitid,
                struct compat_siginfo __user *, infop, int, options,
                struct compat_rusage __user *, uru)
 {
-       siginfo_t info;
        struct rusage ru;
-       long ret;
-       mm_segment_t old_fs = get_fs();
-
-       memset(&info, 0, sizeof(info));
+       struct waitid_info info = {.status = 0};
+       long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
 
-       set_fs(KERNEL_DS);
-       ret = kernel_waitid(which, pid, (siginfo_t __user *)&info, options,
-                        uru ? &ru : NULL);
-       set_fs(old_fs);
-
-       if ((ret < 0) || (info.si_signo == 0))
-               return ret;
-
-       if (uru) {
-               /* sys_waitid() overwrites everything in ru */
+       if (!err && uru) {
+               /* kernel_waitid() overwrites everything in ru */
                if (COMPAT_USE_64BIT_TIME)
-                       ret = copy_to_user(uru, &ru, sizeof(ru));
+                       err = copy_to_user(uru, &ru, sizeof(ru));
                else
-                       ret = put_compat_rusage(&ru, uru);
-               if (ret)
+                       err = put_compat_rusage(&ru, uru);
+               if (err)
                        return -EFAULT;
        }
 
-       BUG_ON(info.si_code & __SI_MASK);
-       info.si_code |= __SI_CHLD;
-       return copy_siginfo_to_user32(infop, &info);
+       if (put_user(err ? 0 : SIGCHLD, &infop->si_signo) ||
+           put_user(0, &infop->si_errno) ||
+           put_user((short)info.cause, &infop->si_code) ||
+           put_user(info.pid, &infop->si_pid) ||
+           put_user(info.uid, &infop->si_uid) ||
+           put_user(info.status, &infop->si_status))
+               err = -EFAULT;
+       return err;
 }
 #endif