[PATCH 5.8 019/118] spi: spi-loopback-test: Fix out-of-bounds read

Greg Kroah-Hartman
2020-09-21T16:43:29Z

From: Vincent Whitchurch <vincent.whitchurch@axis.com>

[ Upstream commit 837ba18dfcd4db21ad58107c65bfe89753aa56d7 ]

The "tx/rx-transfer - crossing PAGE_SIZE" test always fails when
len=131071 and rx_offset >= 5:

spi-loopback-test spi0.0: Running test tx/rx-transfer - crossing PAGE_SIZE
...
with iteration values: len = 131071, tx_off = 0, rx_off = 3
with iteration values: len = 131071, tx_off = 0, rx_off = 4
with iteration values: len = 131071, tx_off = 0, rx_off = 5
loopback strangeness - rx changed outside of allowed range at: ...a4321000
spi_msg@ffffffd5a4157690
frame_length: 131071
actual_length: 131071
spi_transfer@ffffffd5a41576f8
len: 131071
tx_buf: ffffffd5a4340ffc

Note that rx_offset > 3 can only occur if the SPI controller driver sets
->dma_alignment to a higher value than 4, so most SPI controller drivers
are not affect.

The allocated Rx buffer is of size SPI_TEST_MAX_SIZE_PLUS, which is 132
KiB (assuming 4 KiB pages). This test uses an initial offset into the
rx_buf of PAGE_SIZE - 4, and a len of 131071, so the range expected to
be written in this transfer ends at (4096 - 4) + 5 + 131071 == 132 KiB,
which is also the end of the allocated buffer. But the code which
verifies the content of the buffer reads a byte beyond the allocated
buffer and spuriously fails because this out-of-bounds read doesn't
return the expected value.

Fix this by using ITERATE_LEN instead of ITERATE_MAX_LEN to avoid
testing sizes which cause out-of-bounds reads.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20200902132341.7079-1-vincent.whitchurch@axis.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-loopback-test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-loopback-test.c b/drivers/spi/spi-loopback-test.c
index b6d79cd156fb5..da1153ec9f0e3 100644
--- a/drivers/spi/spi-loopback-test.c
+++ b/drivers/spi/spi-loopback-test.c
@@ -90,7 +90,7 @@ static struct spi_test spi_tests[] = {
{
.description = "tx/rx-transfer - crossing PAGE_SIZE",
.fill_option = FILL_COUNT_8,
- .iterate_len = { ITERATE_MAX_LEN },
+ .iterate_len = { ITERATE_LEN },
.iterate_tx_align = ITERATE_ALIGN,
.iterate_rx_align = ITERATE_ALIGN,
.transfer_count = 1,
--
2.25.1