signal: move the "sig < SIGRTMIN" check into siginmask(sig)

commit 5c8ccefdf46c5f87d87b694c7fbc04941c2c99a5 upstream.

All the users of siginmask() must ensure that sig < SIGRTMIN.  sig_fatal()
doesn't and this is wrong:

	UBSAN: Undefined behaviour in kernel/signal.c:911:6
	shift exponent 32 is too large for 32-bit type 'long unsigned int'

the patch doesn't add the neccesary check to sig_fatal(), it moves the
check into siginmask() and updates other callers.

Link: http://lkml.kernel.org/r/20160517195052.GA15187@redhat.com
Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/signal.h b/include/linux/signal.h
index a822300..027a3c5 100644 (file)
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -345,7 +345,9 @@ int unhandled_signal(struct task_struct *tsk, int sig);
 #else
 #define rt_sigmask(sig)        sigmask(sig)
 #endif
-#define siginmask(sig, mask) (rt_sigmask(sig) & (mask))
+
+#define siginmask(sig, mask) \
+       ((sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
 
 #define SIG_KERNEL_ONLY_MASK (\
        rt_sigmask(SIGKILL)   |  rt_sigmask(SIGSTOP))
@@ -366,14 +368,10 @@ int unhandled_signal(struct task_struct *tsk, int sig);
         rt_sigmask(SIGCONT)   |  rt_sigmask(SIGCHLD)   | \
        rt_sigmask(SIGWINCH)  |  rt_sigmask(SIGURG)    )
 
-#define sig_kernel_only(sig) \
-       (((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_ONLY_MASK))
-#define sig_kernel_coredump(sig) \
-       (((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_COREDUMP_MASK))
-#define sig_kernel_ignore(sig) \
-       (((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_IGNORE_MASK))
-#define sig_kernel_stop(sig) \
-       (((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_STOP_MASK))
+#define sig_kernel_only(sig)           siginmask(sig, SIG_KERNEL_ONLY_MASK)
+#define sig_kernel_coredump(sig)       siginmask(sig, SIG_KERNEL_COREDUMP_MASK)
+#define sig_kernel_ignore(sig)         siginmask(sig, SIG_KERNEL_IGNORE_MASK)
+#define sig_kernel_stop(sig)           siginmask(sig, SIG_KERNEL_STOP_MASK)
 
 #define sig_user_defined(t, signr) \
        (((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) &&  \