Messages in this thread Patch in this message | | | From | Wenwen Wang <> | Subject | [PATCH] ethtool: fix a privilege escalation bug | Date | Mon, 8 Oct 2018 10:49:35 -0500 |
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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.
Signed-off-by: Wenwen Wang <wang6495@umn.edu> --- net/core/ethtool.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/core/ethtool.c b/net/core/ethtool.c index c9993c6..ccb337e 100644 --- a/net/core/ethtool.c +++ b/net/core/ethtool.c @@ -2462,13 +2462,17 @@ static int ethtool_set_per_queue_coalesce(struct net_device *dev, 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); @@ -2838,7 +2842,7 @@ 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); -- 2.7.4
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