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/fs/fcntl.c b/fs/fcntl.c
index 0522e283a4f4..c17369659f4a 100644
--- 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;