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authorWenwen Wang <wang6495@umn.edu>2018-10-08 10:49:35 -0500
committerDavid S. Miller <davem@davemloft.net>2018-10-15 21:37:58 -0700
commit58f5bbe331c566f49c9559568f982202a278aa78 (patch)
tree013be2c5db2e21cdfafe6a249d6dac5790627c47 /net/core
parent2bb3207dbbd4d30e96dd0e1c8e013104193bd59c (diff)
ethtool: fix a privilege escalation bug
In dev_ethtool(), the eth command 'ethcmd' is firstly copied from the use-space buffer 'useraddr' and checked to see whether it is ETHTOOL_PERQUEUE. If yes, the sub-command 'sub_cmd' is further copied from the user space. Otherwise, 'sub_cmd' is the same as 'ethcmd'. Next, according to 'sub_cmd', a permission check is enforced through the function ns_capable(). For example, the permission check is required if 'sub_cmd' is ETHTOOL_SCOALESCE, but it is not necessary if 'sub_cmd' is ETHTOOL_GCOALESCE, as suggested in the comment "Allow some commands to be done by anyone". The following execution invokes different handlers according to 'ethcmd'. Specifically, if 'ethcmd' is ETHTOOL_PERQUEUE, ethtool_set_per_queue() is called. In ethtool_set_per_queue(), the kernel object 'per_queue_opt' is copied again from the user-space buffer 'useraddr' and 'per_queue_opt.sub_command' is used to determine which operation should be performed. Given that the buffer 'useraddr' is in the user space, a malicious user can race to change the sub-command between the two copies. In particular, the attacker can supply ETHTOOL_PERQUEUE and ETHTOOL_GCOALESCE to bypass the permission check in dev_ethtool(). Then before ethtool_set_per_queue() is called, the attacker changes ETHTOOL_GCOALESCE to ETHTOOL_SCOALESCE. In this way, the attacker can bypass the permission check and execute ETHTOOL_SCOALESCE. This patch enforces a check in ethtool_set_per_queue() after the second copy from 'useraddr'. If the sub-command is different from the one obtained in the first copy in dev_ethtool(), an error code EINVAL will be returned. Fixes: f38d138a7da6 ("net/ethtool: support set coalesce per queue") Signed-off-by: Wenwen Wang <wang6495@umn.edu> Reviewed-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/ethtool.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 192f2f76b7bd..aeabc4831fca 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -2472,13 +2472,17 @@ roll_back:
return ret;
}
-static int ethtool_set_per_queue(struct net_device *dev, void __user *useraddr)
+static int ethtool_set_per_queue(struct net_device *dev,
+ void __user *useraddr, u32 sub_cmd)
{
struct ethtool_per_queue_op per_queue_opt;
if (copy_from_user(&per_queue_opt, useraddr, sizeof(per_queue_opt)))
return -EFAULT;
+ if (per_queue_opt.sub_command != sub_cmd)
+ return -EINVAL;
+
switch (per_queue_opt.sub_command) {
case ETHTOOL_GCOALESCE:
return ethtool_get_per_queue_coalesce(dev, useraddr, &per_queue_opt);
@@ -2849,7 +2853,7 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
rc = ethtool_get_phy_stats(dev, useraddr);
break;
case ETHTOOL_PERQUEUE:
- rc = ethtool_set_per_queue(dev, useraddr);
+ rc = ethtool_set_per_queue(dev, useraddr, sub_cmd);
break;
case ETHTOOL_GLINKSETTINGS:
rc = ethtool_get_link_ksettings(dev, useraddr);