[PATCH] RISC-V: Avoid dereferening NULL regs in die()

From: Palmer Dabbelt <palmer@rivosinc.com>
To: linux-riscv@lists.infradead.org
Cc: Palmer Dabbelt <palmer@rivosinc.com>,
	kernel test robot <lkp@intel.com>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: [PATCH] RISC-V: Avoid dereferening NULL regs in die()
Date: Tue, 20 Sep 2022 13:00:37 -0700	[thread overview]
Message-ID: <20220920200037.6727-1-palmer@rivosinc.com> (raw)

I don't think we can actually die() without a regs pointer, but the
compiler was warning about a NULL check after a dereference.  It seems
prudent to just avoid the possibly-NULL dereference, given that when
die()ing the system is already toast so who knows how we got there.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 arch/riscv/kernel/traps.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 635e6ec26938..f3e96d60a2ff 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -33,6 +33,7 @@ void die(struct pt_regs *regs, const char *str)
 {
 	static int die_counter;
 	int ret;
+	long cause;
 
 	oops_enter();
 
@@ -42,11 +43,13 @@ void die(struct pt_regs *regs, const char *str)
 
 	pr_emerg("%s [#%d]\n", str, ++die_counter);
 	print_modules();
-	show_regs(regs);
+	if (regs)
+		show_regs(regs);
 
-	ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
+	cause = regs ? regs->cause : -1;
+	ret = notify_die(DIE_OOPS, str, regs, 0, cause, SIGSEGV);
 
-	if (regs && kexec_should_crash(current))
+	if (kexec_should_crash(current))
 		crash_kexec(regs);
 
 	bust_spinlocks(0);
-- 
2.34.1


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