linux-hardening - [PATCH] ARM: vexpress/spc: Avoid negative array index when !SMP

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Date:   Thu, 31 Mar 2022 12:04:43 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Liviu Dudau <liviu.dudau@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] ARM: vexpress/spc: Avoid negative array index when !SMP

When building multi_v7_defconfig+CONFIG_SMP=n, -Warray-bounds exposes
a couple negative array index accesses:

arch/arm/mach-vexpress/spc.c: In function 've_spc_clk_init':
arch/arm/mach-vexpress/spc.c:583:21: warning: array subscript -1 is below array bounds of 'bool[2]' {aka '_Bool[2]'} [-Warray-bounds]
  583 |   if (init_opp_table[cluster])
      |       ~~~~~~~~~~~~~~^~~~~~~~~
arch/arm/mach-vexpress/spc.c:556:7: note: while referencing 'init_opp_table'
  556 |  bool init_opp_table[MAX_CLUSTERS] = { false };
      |       ^~~~~~~~~~~~~~
arch/arm/mach-vexpress/spc.c:592:18: warning: array subscript -1 is below array bounds of 'bool[2]' {aka '_Bool[2]'} [-Warray-bounds]
  592 |    init_opp_table[cluster] = true;
      |    ~~~~~~~~~~~~~~^~~~~~~~~
arch/arm/mach-vexpress/spc.c:556:7: note: while referencing 'init_opp_table'
  556 |  bool init_opp_table[MAX_CLUSTERS] = { false };
      |       ^~~~~~~~~~~~~~

Skip this logic when built !SMP.

Cc: Liviu Dudau <liviu.dudau@....com>
Cc: Sudeep Holla <sudeep.holla@....com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc: Russell King <linux@...linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/mach-vexpress/spc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-vexpress/spc.c b/arch/arm/mach-vexpress/spc.c
index 1da11bdb1dfb..1c6500c4e6a1 100644
--- a/arch/arm/mach-vexpress/spc.c
+++ b/arch/arm/mach-vexpress/spc.c
@@ -580,7 +580,7 @@ static int __init ve_spc_clk_init(void)
 		}

 		cluster = topology_physical_package_id(cpu_dev->id);
-		if (init_opp_table[cluster])
+		if (cluster < 0 || init_opp_table[cluster])
 			continue;

 		if (ve_init_opp_table(cpu_dev))
--
2.32.0