signal: Ensure generic siginfos the kernel sends have all bits initialized

Call clear_siginfo to ensure stack allocated siginfos are fully
initialized before being passed to the signal sending functions.

This ensures that if there is the kind of confusion documented by
TRAP_FIXME, FPE_FIXME, or BUS_FIXME the kernel won't send unitialized
data to userspace when the kernel generates a signal with SI_USER but
the copy to userspace assumes it is a different kind of signal, and
different fields are initialized.

This also prepares the way for turning copy_siginfo_to_user
into a copy_to_user, by removing the need in many cases to perform
a field by field copy simply to skip the uninitialized fields.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 0522e283a4f48c1b5bfc2433de9ad12d82cfc891..c17369659f4a7d9d195f218bdba38030ba43d582 100644 (file)
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -737,6 +737,7 @@ static void send_sigio_to_task(struct task_struct *p,
                           delivered even if we can't queue.  Failure to
                           queue in this case _should_ be reported; we fall
                           back to SIGIO in that case. --sct */
+                       clear_siginfo(&si);
                        si.si_signo = signum;
                        si.si_errno = 0;
                        si.si_code  = reason;

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 9649ecd8a73a704fe07e3d678ac96723d33aec05..17bc8b874d925b5ff0fbe041567cce99fba04e73 100644 (file)
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -639,6 +639,7 @@ static void __do_notify(struct mqueue_inode_info *info)
                case SIGEV_SIGNAL:
                        /* sends signal */
 
+                       clear_siginfo(&sig_i);
                        sig_i.si_signo = info->notify.sigev_signo;
                        sig_i.si_errno = 0;
                        sig_i.si_code = SI_MESGQ;

diff --git a/kernel/signal.c b/kernel/signal.c
index fd182a845490fe979d6b64de1151c3366ff96216..241d54958bbbcef16dcbb78b1a96ebd33c75694c 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -549,6 +549,7 @@ static void collect_signal(int sig, struct sigpending *list, siginfo_t *info,
                 * a fast-pathed signal or we must have been
                 * out of queue space.  So zero out the info.
                 */
+               clear_siginfo(info);
                info->si_signo = sig;
                info->si_errno = 0;
                info->si_code = SI_USER;
@@ -1043,6 +1044,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
                list_add_tail(&q->list, &pending->list);
                switch ((unsigned long) info) {
                case (unsigned long) SEND_SIG_NOINFO:
+                       clear_siginfo(&q->info);
                        q->info.si_signo = sig;
                        q->info.si_errno = 0;
                        q->info.si_code = SI_USER;
@@ -1051,6 +1053,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
                        q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
                        break;
                case (unsigned long) SEND_SIG_PRIV:
+                       clear_siginfo(&q->info);
                        q->info.si_signo = sig;
                        q->info.si_errno = 0;
                        q->info.si_code = SI_KERNEL;
@@ -1623,6 +1626,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
                        sig = SIGCHLD;
        }
 
+       clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        /*
@@ -1717,6 +1721,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk,
                parent = tsk->real_parent;
        }
 
+       clear_siginfo(&info);
        info.si_signo = SIGCHLD;
        info.si_errno = 0;
        /*
@@ -1929,7 +1934,7 @@ static void ptrace_do_notify(int signr, int exit_code, int why)
 {
        siginfo_t info;
 
-       memset(&info, 0, sizeof info);
+       clear_siginfo(&info);
        info.si_signo = signr;
        info.si_code = exit_code;
        info.si_pid = task_pid_vnr(current);
@@ -2136,6 +2141,7 @@ static int ptrace_signal(int signr, siginfo_t *info)
         * have updated *info via PTRACE_SETSIGINFO.
         */
        if (signr != info->si_signo) {
+               clear_siginfo(info);
                info->si_signo = signr;
                info->si_errno = 0;
                info->si_code = SI_USER;
@@ -2941,6 +2947,7 @@ SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
 {
        struct siginfo info;
 
+       clear_siginfo(&info);
        info.si_signo = sig;
        info.si_errno = 0;
        info.si_code = SI_USER;