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>

1 files changed, 1 insertions, 0 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 9649ecd8a73a..17bc8b874d92 100644
--- 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;