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

From: Oleg Nesterov
Date: Tue May 17 2016 - 15:50:59 EST


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

[ 211.406327] UBSAN: Undefined behaviour in kernel/signal.c:911:6
[ 211.406365] 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.

Reported-by: Meelis Roos <mroos@xxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
include/linux/signal.h | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/include/linux/signal.h b/include/linux/signal.h
index 92557bb..101bba8 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -385,7 +385,9 @@ 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))
@@ -406,14 +408,10 @@ 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) && \
--
2.5.0