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ptp: fix Spectre v1 vulnerability

PATCH Applied Gustavo A. R. Silva 3 participants 3 messages Oct 16, 2018 – Oct 18, 2018

Subsystems (3)
Networking Network drivers PTP hardware clock support
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Gustavo A. R. Silva

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#0 lore raw

PATCH 1/1 ptp: fix Spectre v1 vulnerability

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

Cc [email protected]
Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 drivers/ptp/ptp_chardev.c | 4 ++++
 1 file changed, 4 insertions(+)
drivers/ptp/ptp_chardev.c +4 -0
index 01b0e2b..2012551 100644
@@ -24,6 +24,8 @@
 #include <linux/slab.h>
 #include <linux/timekeeping.h>
 
+#include <linux/nospec.h>
+
 #include "ptp_private.h"
 
 static int ptp_disable_pinfunc(struct ptp_clock_info *ops,

@@ -248,6 +250,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			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];

@@ -266,6 +269,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			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);
Signature · 1 line
2.7.4
maintainer Acked-by on v1 1/1
#1 lore raw
Quoted 5 lines · Gustavo A. R. Silva

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:

Quoted 7 lines

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.

Acked-by Richard Cochran <[email protected]>
maintainer Applied
#2 lore raw
In reply to Gustavo A. R. Silva

From: "Gustavo A. R. Silva" <[email protected]>
Date: Tue, 16 Oct 2018 15:06:41 +0200

Quoted 13 lines

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.

Quoted 8 lines

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]>

Applied.