| Message ID | 75854affc1923309fde05e47494263bde73e5592.1621703210.git.lukas@wunner.de |
|---|---|
| State | Accepted |
| Commit | 13817d466eb8713a1ffd254f537402f091d48444 |
| Headers | show |
| Series | [for-5.13] spi: bcm2835: Fix out-of-bounds access with more than 4 slaves | expand |
On Sat, 22 May 2021 19:49:50 +0200, Lukas Wunner wrote: > Commit 571e31fa60b3 ("spi: bcm2835: Cache CS register value for > ->prepare_message()") limited the number of slaves to 3 at compile-time. > The limitation was necessitated by a statically-sized array prepare_cs[] > in the driver private data which contains a per-slave register value. > > The commit sought to enforce the limitation at run-time by setting the > controller's num_chipselect to 3: Slaves with a higher chipselect are > rejected by spi_add_device(). > > [...] Applied to https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next Thanks! [1/1] spi: bcm2835: Fix out-of-bounds access with more than 4 slaves commit: 13817d466eb8713a1ffd254f537402f091d48444 All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted. You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed. If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced. Please add any relevant lists and maintainers to the CCs when replying to this mail. Thanks, Mark
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index 8965fe61c8b4..fe40626e45aa 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -68,7 +68,7 @@ #define BCM2835_SPI_FIFO_SIZE 64 #define BCM2835_SPI_FIFO_SIZE_3_4 48 #define BCM2835_SPI_DMA_MIN_LENGTH 96 -#define BCM2835_SPI_NUM_CS 4 /* raise as necessary */ +#define BCM2835_SPI_NUM_CS 24 /* raise as necessary */ #define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ | SPI_NO_CS | SPI_3WIRE) @@ -1195,6 +1195,12 @@ static int bcm2835_spi_setup(struct spi_device *spi) struct gpio_chip *chip; u32 cs; + if (spi->chip_select >= BCM2835_SPI_NUM_CS) { + dev_err(&spi->dev, "only %d chip-selects supported\n", + BCM2835_SPI_NUM_CS - 1); + return -EINVAL; + } + /* * Precalculate SPI slave's CS register value for ->prepare_message(): * The driver always uses software-controlled GPIO chip select, hence @@ -1288,7 +1294,7 @@ static int bcm2835_spi_probe(struct platform_device *pdev) ctlr->use_gpio_descriptors = true; ctlr->mode_bits = BCM2835_SPI_MODE_BITS; ctlr->bits_per_word_mask = SPI_BPW_MASK(8); - ctlr->num_chipselect = BCM2835_SPI_NUM_CS; + ctlr->num_chipselect = 3; ctlr->setup = bcm2835_spi_setup; ctlr->transfer_one = bcm2835_spi_transfer_one; ctlr->handle_err = bcm2835_spi_handle_err;
Commit 571e31fa60b3 ("spi: bcm2835: Cache CS register value for ->prepare_message()") limited the number of slaves to 3 at compile-time. The limitation was necessitated by a statically-sized array prepare_cs[] in the driver private data which contains a per-slave register value. The commit sought to enforce the limitation at run-time by setting the controller's num_chipselect to 3: Slaves with a higher chipselect are rejected by spi_add_device(). However the commit neglected that num_chipselect only limits the number of *native* chipselects. If GPIO chipselects are specified in the device tree for more than 3 slaves, num_chipselect is silently raised by of_spi_get_gpio_numbers() and the result are out-of-bounds accesses to the statically-sized array prepare_cs[]. As a bandaid fix which is backportable to stable, raise the number of allowed slaves to 24 (which "ought to be enough for anybody"), enforce the limitation on slave ->setup and revert num_chipselect to 3 (which is the number of native chipselects supported by the controller). An upcoming for-next commit will allow an arbitrary number of slaves. Fixes: 571e31fa60b3 ("spi: bcm2835: Cache CS register value for ->prepare_message()") Reported-by: Joe Burmeister <joe.burmeister@devtank.co.uk> Signed-off-by: Lukas Wunner <lukas@wunner.de> Cc: stable@vger.kernel.org # v5.4+ Cc: Phil Elwell <phil@raspberrypi.com> --- drivers/spi/spi-bcm2835.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)