ipmi: msghandler: Fix potential Spectre v1 vulnerabilities

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@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index a74ce885b54125b3852cd9f7de66ec5ee2a52ea3..7a9fbe60a8406cf6a13e058ee41a758c4fb1afc7 100644 (file)
--- 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 *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 *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 *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].lun = LUN & 0x3;
+       }
        release_ipmi_user(user, index);
 
        return rv;
@@ -1358,10 +1365,12 @@ int ipmi_get_my_LUN(struct ipmi_user *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].lun;
+       }
        release_ipmi_user(user, index);
 
        return rv;
@@ -2184,6 +2193,7 @@ static int check_addr(struct ipmi_smi  *intf,
 {
        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;