From: Hugo Villeneuve hvilleneuve@dimonoff.com

commit dbf4ab821804df071c8b566d9813083125e6d97b upstream.

The SC16IS7XX IC supports a burst mode to access the FIFOs where the initial register address is sent ($00), followed by all the FIFO data without having to resend the register address each time. In this mode, the IC doesn't increment the register address for each R/W byte.

The regmap_raw_read() and regmap_raw_write() are functions which can perform IO over multiple registers. They are currently used to read/write from/to the FIFO, and although they operate correctly in this burst mode on the SPI bus, they would corrupt the regmap cache if it was not disabled manually. The reason is that when the R/W size is more than 1 byte, these functions assume that the register address is incremented and handle the cache accordingly.

Convert FIFO R/W functions to use the regmap _noinc_ versions in order to remove the manual cache control which was a workaround when using the _raw_ versions. FIFO registers are properly declared as volatile so cache will not be used/updated for FIFO accesses.

Fixes: dfeae619d781 ("serial: sc16is7xx") Cc: stable@vger.kernel.org # 5.10 5.15 Signed-off-by: Hugo Villeneuve hvilleneuve@dimonoff.com Link: https://lore.kernel.org/r/20231211171353.2901416-6-hugo@hugovil.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Hugo Villeneuve hvilleneuve@dimonoff.com Signed-off-by: GONG, Ruiqi gongruiqi1@huawei.com ---

v2: Backport to both 5.15 and 5.10

The mainline commit dbf4ab821804 ("serial: sc16is7xx: convert from _raw_ to _noinc_ regmap functions for FIFO") by Hugo has been assigned to be CVE-2023-52488, but for stable branches lower than 6.1 there's no official backport.

I made up this backport patch for 5.10, and its correctness has been confirmed in previous communication with Hugo. Let's publicize it and merge it into upstream.

drivers/tty/serial/sc16is7xx.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index 8c09c97f9814..0066a0e23516 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -376,9 +376,7 @@ static void sc16is7xx_fifo_read(struct uart_port *port, unsigned int rxlen) const u8 line = sc16is7xx_line(port); u8 addr = (SC16IS7XX_RHR_REG << SC16IS7XX_REG_SHIFT) | line;

- regcache_cache_bypass(s->regmap, true); - regmap_raw_read(s->regmap, addr, s->buf, rxlen); - regcache_cache_bypass(s->regmap, false); + regmap_noinc_read(s->regmap, addr, s->buf, rxlen); }

static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send) @@ -394,9 +392,7 @@ static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send) if (unlikely(!to_send)) return;

- regcache_cache_bypass(s->regmap, true); - regmap_raw_write(s->regmap, addr, s->buf, to_send); - regcache_cache_bypass(s->regmap, false); + regmap_noinc_write(s->regmap, addr, s->buf, to_send); }

static void sc16is7xx_port_update(struct uart_port *port, u8 reg, @@ -489,6 +485,11 @@ static bool sc16is7xx_regmap_precious(struct device *dev, unsigned int reg) return false; }

+static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg) +{ + return reg == SC16IS7XX_RHR_REG; +} + static int sc16is7xx_set_baud(struct uart_port *port, int baud) { struct sc16is7xx_port *s = dev_get_drvdata(port->dev); @@ -1439,6 +1440,8 @@ static struct regmap_config regcfg = { .cache_type = REGCACHE_RBTREE, .volatile_reg = sc16is7xx_regmap_volatile, .precious_reg = sc16is7xx_regmap_precious, + .writeable_noinc_reg = sc16is7xx_regmap_noinc, + .readable_noinc_reg = sc16is7xx_regmap_noinc, };

#ifdef CONFIG_SERIAL_SC16IS7XX_SPI