From: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon, 6 Mar 2023 01:20:30 +0000 (+0000)
Subject: sh: sanitize the flags on sigreturn
X-Git-Tag: baikal/mips/sdk5.8.2~65
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=a7d0c43b23ffb3f8033c199841ffd5b0011302e1;p=kernel.git

sh: sanitize the flags on sigreturn

[ Upstream commit 573b22ccb7ce9ab7f0539a2e11a9d3609a8783f5 ]

We fetch %SR value from sigframe; it might have been modified by signal
handler, so we can't trust it with any bits that are not modifiable in
user mode.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Rich Felker <dalias@libc.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/arch/sh/include/asm/processor_32.h b/arch/sh/include/asm/processor_32.h
index 0e0ecc0132e3b..58ae979798fa8 100644
--- a/arch/sh/include/asm/processor_32.h
+++ b/arch/sh/include/asm/processor_32.h
@@ -51,6 +51,7 @@
 #define SR_FD		0x00008000
 #define SR_MD		0x40000000
 
+#define SR_USER_MASK	0x00000303	// M, Q, S, T bits
 /*
  * DSP structure and data
  */
diff --git a/arch/sh/kernel/signal_32.c b/arch/sh/kernel/signal_32.c
index 24473fa6c3b63..f6e1a47ad7ca0 100644
--- a/arch/sh/kernel/signal_32.c
+++ b/arch/sh/kernel/signal_32.c
@@ -116,6 +116,7 @@ static int
 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *r0_p)
 {
 	unsigned int err = 0;
+	unsigned int sr = regs->sr & ~SR_USER_MASK;
 
 #define COPY(x)		err |= __get_user(regs->x, &sc->sc_##x)
 			COPY(regs[1]);
@@ -131,6 +132,8 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *r0_p
 	COPY(sr);	COPY(pc);
 #undef COPY
 
+	regs->sr = (regs->sr & SR_USER_MASK) | sr;
+
 #ifdef CONFIG_SH_FPU
 	if (boot_cpu_data.flags & CPU_HAS_FPU) {
 		int owned_fp;