3.16.62-rc1 review patch. If anyone has any objections, please let me know.
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From: "Gustavo A. R. Silva" gustavo@embeddedor.com
commit efa61c8cf2950ab5c0e66cff3cabe2a2b24e81ba upstream.
pin_index can be 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/ptp/ptp_chardev.c:253 ptp_ioctl() warn: potential spectre issue 'ops->pin_config' [r] (local cap)
Fix this by sanitizing pin_index before using it to index ops->pin_config, and before passing it as an argument to function ptp_set_pinfunc(), in which it is used to index info->pin_config.
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
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Acked-by: Richard Cochran richardcochran@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/ptp/ptp_chardev.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -23,6 +23,8 @@ #include <linux/sched.h> #include <linux/slab.h>
+#include <linux/nospec.h> + #include "ptp_private.h"
static int ptp_disable_pinfunc(struct ptp_clock_info *ops, @@ -228,6 +230,7 @@ long ptp_ioctl(struct posix_clock *pc, u err = -EINVAL; break; } + pin_index = array_index_nospec(pin_index, ops->n_pins); if (mutex_lock_interruptible(&ptp->pincfg_mux)) return -ERESTARTSYS; pd = ops->pin_config[pin_index]; @@ -246,6 +249,7 @@ long ptp_ioctl(struct posix_clock *pc, u err = -EINVAL; break; } + pin_index = array_index_nospec(pin_index, ops->n_pins); if (mutex_lock_interruptible(&ptp->pincfg_mux)) return -ERESTARTSYS; err = ptp_set_pinfunc(ptp, pin_index, pd.func, pd.chan);