linux-kernel - [PATCH 4.20 125/127] ipmi: msghandler: Fix potential Spectre v1 vulnerabilities

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Date:   Thu, 24 Jan 2019 20:21:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Corey Minyard <cminyard@...sta.com>
Subject: [PATCH 4.20 125/127] ipmi: msghandler: Fix potential Spectre v1 vulnerabilities

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gustavo A. R. Silva <gustavo@...eddedor.com>

commit a7102c7461794a5bb31af24b08e9e0f50038897a upstream.

channel and addr->channel are indirectly controlled by user-space,
hence leading to a potential exploitation of the Spectre variant 1
vulnerability.

These issues were detected with the help of Smatch:

drivers/char/ipmi/ipmi_msghandler.c:1381 ipmi_set_my_address() warn: potential spectre issue 'user->intf->addrinfo' [w] (local cap)
drivers/char/ipmi/ipmi_msghandler.c:1401 ipmi_get_my_address() warn: potential spectre issue 'user->intf->addrinfo' [r] (local cap)
drivers/char/ipmi/ipmi_msghandler.c:1421 ipmi_set_my_LUN() warn: potential spectre issue 'user->intf->addrinfo' [w] (local cap)
drivers/char/ipmi/ipmi_msghandler.c:1441 ipmi_get_my_LUN() warn: potential spectre issue 'user->intf->addrinfo' [r] (local cap)
drivers/char/ipmi/ipmi_msghandler.c:2260 check_addr() warn: potential spectre issue 'intf->addrinfo' [r] (local cap)

Fix this by sanitizing channel and addr->channel before using them to
index user->intf->addrinfo and intf->addrinfo, correspondingly.

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://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/

Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
Signed-off-by: Corey Minyard <cminyard@...sta.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/ipmi/ipmi_msghandler.c |   26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -32,6 +32,7 @@
 #include <linux/moduleparam.h>
 #include <linux/workqueue.h>
 #include <linux/uuid.h>
+#include <linux/nospec.h>
 
 #define IPMI_DRIVER_VERSION "39.2"
 
@@ -1298,10 +1299,12 @@ int ipmi_set_my_address(struct ipmi_user
 	if (!user)
 		return -ENODEV;
 
-	if (channel >= IPMI_MAX_CHANNELS)
+	if (channel >= IPMI_MAX_CHANNELS) {
 		rv = -EINVAL;
-	else
+	} else {
+		channel = array_index_nospec(channel, IPMI_MAX_CHANNELS);
 		user->intf->addrinfo[channel].address = address;
+	}
 	release_ipmi_user(user, index);
 
 	return rv;
@@ -1318,10 +1321,12 @@ int ipmi_get_my_address(struct ipmi_user
 	if (!user)
 		return -ENODEV;
 
-	if (channel >= IPMI_MAX_CHANNELS)
+	if (channel >= IPMI_MAX_CHANNELS) {
 		rv = -EINVAL;
-	else
+	} else {
+		channel = array_index_nospec(channel, IPMI_MAX_CHANNELS);
 		*address = user->intf->addrinfo[channel].address;
+	}
 	release_ipmi_user(user, index);
 
 	return rv;
@@ -1338,10 +1343,12 @@ int ipmi_set_my_LUN(struct ipmi_user *us
 	if (!user)
 		return -ENODEV;
 
-	if (channel >= IPMI_MAX_CHANNELS)
+	if (channel >= IPMI_MAX_CHANNELS) {
 		rv = -EINVAL;
-	else
+	} else {
+		channel = array_index_nospec(channel, IPMI_MAX_CHANNELS);
 		user->intf->addrinfo[channel].lun = LUN & 0x3;
+	}
 	release_ipmi_user(user, index);
 
 	return rv;
@@ -1358,10 +1365,12 @@ int ipmi_get_my_LUN(struct ipmi_user *us
 	if (!user)
 		return -ENODEV;
 
-	if (channel >= IPMI_MAX_CHANNELS)
+	if (channel >= IPMI_MAX_CHANNELS) {
 		rv = -EINVAL;
-	else
+	} else {
+		channel = array_index_nospec(channel, IPMI_MAX_CHANNELS);
 		*address = user->intf->addrinfo[channel].lun;
+	}
 	release_ipmi_user(user, index);
 
 	return rv;
@@ -2184,6 +2193,7 @@ static int check_addr(struct ipmi_smi  *
 {
 	if (addr->channel >= IPMI_MAX_CHANNELS)
 		return -EINVAL;
+	addr->channel = array_index_nospec(addr->channel, IPMI_MAX_CHANNELS);
 	*lun = intf->addrinfo[addr->channel].lun;
 	*saddr = intf->addrinfo[addr->channel].address;
 	return 0;