linux-kernel - [PATCH 3.2 02/61] signal: move the "sig < SIGRTMIN" check into siginmask(sig)

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Message-ID: <lsq.1511316665.444125315@decadent.org.uk>
Date:   Wed, 22 Nov 2017 02:11:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Oleg Nesterov" <oleg@...hat.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Meelis Roos" <mroos@...ux.ee>
Subject: [PATCH 3.2 02/61] signal: move the "sig < SIGRTMIN" check into
 siginmask(sig)

3.2.96-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Oleg Nesterov <oleg@...hat.com>

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@...ux.ee>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/signal.h | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -345,7 +345,9 @@ int unhandled_signal(struct task_struct
 #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
         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) &&	\