3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Emese Revfy <[email protected]>

commit b9e146d8eb3b9ecae5086d373b50fa0c1f3e7f0f upstream.

This fixes a kernel memory contents leak via the tkill and tgkill syscalls
for compat processes.

This is visible in the siginfo_t->_sifields._rt.si_sigval.sival_ptr field
when handling signals delivered from tkill.

The place of the infoleak:

int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from)
{
        ...
        put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
        ...
}

Signed-off-by: Emese Revfy <[email protected]>
Reviewed-by: PaX Team <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Serge Hallyn <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 kernel/signal.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2867,7 +2867,7 @@ do_send_specific(pid_t tgid, pid_t pid,
 
 static int do_tkill(pid_t tgid, pid_t pid, int sig)
 {
-       struct siginfo info;
+       struct siginfo info = {};
 
        info.si_signo = sig;
        info.si_errno = 0;


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