linux-hardening - [PATCH v6 3/4] powerpc: Use WARN_ON and fix check in poking

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Date:   Fri, 10 Sep 2021 21:29:03 -0500
From:   "Christopher M. Riedl" <cmr@...escreens.de>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-hardening@...r.kernel.org
Subject: [PATCH v6 3/4] powerpc: Use WARN_ON and fix check in poking_init

The latest kernel docs list BUG_ON() as 'deprecated' and that they
should be replaced with WARN_ON() (or pr_warn()) when possible. The
BUG_ON() in poking_init() warrants a WARN_ON() rather than a pr_warn()
since the error condition is deemed "unreachable".

Also take this opportunity to fix the failure check in the WARN_ON():
cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, ...) returns a positive integer
on success and a negative integer on failure.

Signed-off-by: Christopher M. Riedl <cmr@...escreens.de>

---

v6:  * New to series - based on Christophe's relentless feedback in the
       crusade against BUG_ON()s :)
---
 arch/powerpc/lib/code-patching.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 8d0bb86125d5..e802e42c2789 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -126,16 +126,11 @@ static int text_area_cpu_down(unsigned int cpu)
 	return 0;
 }

-/*
- * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and
- * we judge it as being preferable to a kernel that will crash later when
- * someone tries to use patch_instruction().
- */
 void __init poking_init(void)
 {
-	BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+	WARN_ON(cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 		"powerpc/text_poke:online", text_area_cpu_up,
-		text_area_cpu_down));
+		text_area_cpu_down) < 0);
 }

 /*
-- 
2.32.0