[PATCH 5.15 035/145] RISC-V: Avoid dereferening NULL regs in die()

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From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

[ Upstream commit f2913d006fcdb61719635e093d1b5dd0dafecac7 ]

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@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220920200037.6727-1-palmer@xxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Stable-dep-of: 130aee3fd998 ("riscv: Avoid enabling interrupts in die()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 6084bd93d2f58..502cba5029ca4 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);
-- 
2.39.2






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