linux-kernel - [PATCH 14/22] spi: amd: Fix out-of-bounds stack access in amd_set_spi

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Message-ID: <78fef0f2434f35be9095bcc9ffa23dd8cab667b9.1742852847.git.jpoimboe@kernel.org>
Date: Mon, 24 Mar 2025 14:56:04 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Brendan Jackman <jackmanb@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Raju Rangoju <Raju.Rangoju@....com>,
	Mark Brown <broonie@...nel.org>,
	kernel test robot <lkp@...el.com>
Subject: [PATCH 14/22] spi: amd: Fix out-of-bounds stack access in amd_set_spi_freq()

If speed_hz < AMD_SPI_MIN_HZ, amd_set_spi_freq() iterates over the
entire amd_spi_freq array without breaking out early, causing 'i' to go
beyond the array bounds.

Fix that by stopping the loop when it gets to the last entry, so the low
speed_hz value gets clamped up to AMD_SPI_MIN_HZ.

Fixes the following warning with an UBSAN kernel:

  drivers/spi/spi-amd.o: error: objtool: amd_set_spi_freq() falls through to next function amd_spi_set_opcode()

Cc: Raju Rangoju <Raju.Rangoju@....com>
CC: Mark Brown <broonie@...nel.org>
Fixes: 3fe26121dc3a ("spi: amd: Configure device speed")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/r/202503161828.RUk9EhWx-lkp@intel.com/
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 drivers/spi/spi-amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-amd.c b/drivers/spi/spi-amd.c
index c85997478b81..17fc0b17e756 100644
--- a/drivers/spi/spi-amd.c
+++ b/drivers/spi/spi-amd.c
@@ -302,7 +302,7 @@ static void amd_set_spi_freq(struct amd_spi *amd_spi, u32 speed_hz)
 {
 	unsigned int i, spd7_val, alt_spd;
 
-	for (i = 0; i < ARRAY_SIZE(amd_spi_freq); i++)
+	for (i = 0; i < ARRAY_SIZE(amd_spi_freq)-1; i++)
 		if (speed_hz >= amd_spi_freq[i].speed_hz)
 			break;
 
-- 
2.48.1