[PATCH 6.1 1/1] objtool, spi: amd: Fix out-of-bounds stack access in amd_set_spi_freq()

[Dmitriy Privalov]

From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

commit 76e51db43fe4aaaebcc5ddda67b0807f7c9bdecc upstream.

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()

Fixes: 3fe26121dc3a ("spi: amd: Configure device speed")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: Raju Rangoju <Raju.Rangoju@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/78fef0f2434f35be9095bcc9ffa23dd8cab667b9.1742852847.git.jpoimboe@xxxxxxxxxx
Closes: https://lore.kernel.org/r/202503161828.RUk9EhWx-lkp@xxxxxxxxx/
Signed-off-by: Dmitriy Privalov <d.privalov@xxxxxx>
---
 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 bfc3ab5f39ea..b53301e563bc 100644
--- a/drivers/spi/spi-amd.c
+++ b/drivers/spi/spi-amd.c
@@ -243,7 +243,7 @@ static int amd_set_spi_freq(struct amd_spi *amd_spi, u32 speed_hz)
 	if (speed_hz < AMD_SPI_MIN_HZ)
 		return -EINVAL;
 
-	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;
 
-- 
2.34.1