[PATCH AUTOSEL 6.2 28/30] sh: sanitize the flags on sigreturn

Sasha Levin
2023-03-20T00:56:06Z

From: Al Viro <viro@zeniv.linux.org.uk>

[ 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>
---
arch/sh/include/asm/processor_32.h | 1 +
arch/sh/kernel/signal_32.c | 3 +++
2 files changed, 4 insertions(+)

diff --git a/arch/sh/include/asm/processor_32.h b/arch/sh/include/asm/processor_32.h
index 27aebf1e75a20..3ef7adf739c83 100644
--- a/arch/sh/include/asm/processor_32.h
+++ b/arch/sh/include/asm/processor_32.h
@@ -50,6 +50,7 @@
#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 90f495d35db29..a6bfc6f374911 100644
--- a/arch/sh/kernel/signal_32.c
+++ b/arch/sh/kernel/signal_32.c
@@ -115,6 +115,7 @@ 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]);
@@ -130,6 +131,8 @@ 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;
--
2.39.2