linux-hardening - [PATCH][next] ARM: OMAP2+: Fix -Warray-bounds warning in _pwrdm_state

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Date:   Wed, 7 Jun 2023 22:12:11 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Peter 'p2' De Schrijver <peter.de-schrijver@...ia.com>,
        Kevin Hilman <khilman@...prootsystems.com>
Cc:     linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] ARM: OMAP2+: Fix -Warray-bounds warning in
 _pwrdm_state_switch()

If function pwrdm_read_prev_pwrst() returns -EINVAL, we will end
up accessing array pwrdm->state_counter through negative index
-22. This is wrong and the compiler is legitimately warning us
about this potential problem.

Fix this by sanity checking the value stored in variable _prev_
before accessing array pwrdm->state_counter.

Address the following -Warray-bounds warning:
arch/arm/mach-omap2/powerdomain.c:178:45: warning: array subscript -22 is below array bounds of 'unsigned int[4]' [-Warray-bounds]

Link: https://github.com/KSPP/linux/issues/307
Fixes: ba20bb126940 ("OMAP: PM counter infrastructure.")
Cc: stable@...r.kernel.org
Reported-by: kernel test robot <lkp@...el.com>
Link: https://lore.kernel.org/lkml/20230607050639.LzbPn%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 arch/arm/mach-omap2/powerdomain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
index 777f9f8e7cd8..5e05dd1324e7 100644
--- a/arch/arm/mach-omap2/powerdomain.c
+++ b/arch/arm/mach-omap2/powerdomain.c
@@ -174,7 +174,7 @@ static int _pwrdm_state_switch(struct powerdomain *pwrdm, int flag)
 		break;
 	case PWRDM_STATE_PREV:
 		prev = pwrdm_read_prev_pwrst(pwrdm);
-		if (pwrdm->state != prev)
+		if (prev >= 0 && pwrdm->state != prev)
 			pwrdm->state_counter[prev]++;
 		if (prev == PWRDM_POWER_RET)
 			_update_logic_membank_counters(pwrdm);
-- 
2.34.1