offset and lineinfo.line_offset are indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability.
This issue was detected with the help of Smatch: drivers/gpio/gpiolib.c:580 linehandle_create() warn: potential spectre issue 'gdev->descs' [r] (local cap) drivers/gpio/gpiolib.c:927 lineevent_create() warn: potential spectre issue 'gdev->descs' [r] (local cap) drivers/gpio/gpiolib.c:1053 gpio_ioctl() warn: potential spectre issue 'gdev->descs' [r] (local cap) Fix this by sanitizing both offset and lineinfo.line_offset before using them to index gdev->descs. Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Cc: [email protected] Signed-off-by: Gustavo A. R. Silva <[email protected]> --- drivers/gpio/gpiolib.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index fc36dc358716..73a0a550162e 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -29,6 +29,8 @@ #include <linux/timekeeping.h> #include <uapi/linux/gpio.h> +#include <linux/nospec.h> + #include "gpiolib.h" #define CREATE_TRACE_POINTS @@ -576,6 +578,7 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip) ret = -EINVAL; goto out_free_descs; } + offset = array_index_nospec(offset, gdev->ngpio); desc = &gdev->descs[offset]; ret = gpiod_request(desc, lh->label); @@ -910,6 +913,7 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip) ret = -EINVAL; goto out_free_label; } + offset = array_index_nospec(offset, gdev->ngpio); /* Return an error if a unknown flag is set */ if ((lflags & ~GPIOHANDLE_REQUEST_VALID_FLAGS) || @@ -1049,6 +1053,8 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) return -EFAULT; if (lineinfo.line_offset >= gdev->ngpio) return -EINVAL; + lineinfo.line_offset = array_index_nospec(lineinfo.line_offset, + gdev->ngpio); desc = &gdev->descs[lineinfo.line_offset]; if (desc->name) { -- 2.19.2
