linux-kernel - [RFC] spi: Prevent unexpected SPI time out due to arithmetic overflow

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 29 Aug 2016 09:02:47 -0500
From:   Sien Wu <sien.wu@...com>
To:     broonie@...nel.org
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sien Wu <sien.wu@...com>
Subject: [RFC] spi: Prevent unexpected SPI time out due to arithmetic overflow

When reading SPI flash as MTD device, the transfer length is
directly passed to the spi driver. If the requested data size
exceeds 512KB, it will cause the time out calculation to
overflow since transfer length is 32-bit unsigned integer.
This issue is resolved by using 64-bit unsigned integer
to perform the arithmetic.

Signed-off-by: Sien Wu <sien.wu@...com>
Acked-by: Brad Keryan <brad.keryan@...com>
Acked-by: Gratian Crisan <gratian.crisan@...com>
Acked-by: Brad Mouring <brad.mouring@...com>

Natinst-ReviewBoard-ID 150232
---
 drivers/spi/spi.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 029dbd3..a186a62 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -678,7 +678,7 @@ static int spi_transfer_one_message(struct spi_master *master,
 	struct spi_transfer *xfer;
 	bool keep_cs = false;
 	int ret = 0;
-	unsigned long ms = 1;
+	unsigned long long ms = 1;
 
 	spi_set_cs(msg->spi, true);
 
@@ -697,11 +697,16 @@ static int spi_transfer_one_message(struct spi_master *master,
 
 			if (ret > 0) {
 				ret = 0;
-				ms = xfer->len * 8 * 1000 / xfer->speed_hz;
+
+				ms = 8LL * 1000LL * xfer->len;
+				do_div(ms, xfer->speed_hz);
 				ms += ms + 100; /* some tolerance */
 
+				if (ms > UINT_MAX)
+					ms = UINT_MAX;
+
 				ms = wait_for_completion_timeout(&master->xfer_completion,
-								 msecs_to_jiffies(ms));
+							msecs_to_jiffies(ms));
 			}
 
 			if (ms == 0) {
-- 
1.7.1