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net: socket: fix a missing-check bug

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In ethtool_ioctl(), the ioctl command 'ethcmd' is checked through a switch
statement to see whether it is necessary to pre-process the ethtool
structure, because, as mentioned in the comment, the structure
ethtool_rxnfc is defined with padding. If yes, a user-space buffer 'rxnfc'
is allocated through compat_alloc_user_space(). One thing to note here is
that, if 'ethcmd' is ETHTOOL_GRXCLSRLALL, the size of the buffer 'rxnfc' is
partially determined by 'rule_cnt', which is actually acquired from the
user-space buffer 'compat_rxnfc', i.e., 'compat_rxnfc->rule_cnt', through
get_user(). After 'rxnfc' is allocated, the data in the original user-space
buffer 'compat_rxnfc' is then copied to 'rxnfc' through copy_in_user(),
including the 'rule_cnt' field. However, after this copy, no check is
re-enforced on 'rxnfc->rule_cnt'. So it is possible that a malicious user
race to change the value in the 'compat_rxnfc->rule_cnt' between these two
copies. Through this way, the attacker can bypass the previous check on
'rule_cnt' and inject malicious data. This can cause undefined behavior of
the kernel and introduce potential security risk.

This patch avoids the above issue via copying the value acquired by
get_user() to 'rxnfc->rule_cn', if 'ethcmd' is ETHTOOL_GRXCLSRLALL.

Signed-off-by: Wenwen Wang <wang6495@umn.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wenwen Wang 2018-10-18 09:36:46 -05:00 committed by David S. Miller
parent 3c53ed8fef
commit b6168562c8
1 changed files with 8 additions and 3 deletions
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9
net/socket.c
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@ -2875,8 +2875,13 @@ static int ethtool_ioctl(struct net *net, struct compat_ifreq __user *ifr32)
copy_in_user(&rxnfc->fs.ring_cookie,
&compat_rxnfc->fs.ring_cookie,
(void __user *)(&rxnfc->fs.location + 1) -
(void __user *)&rxnfc->fs.ring_cookie) ||
copy_in_user(&rxnfc->rule_cnt, &compat_rxnfc->rule_cnt,
(void __user *)&rxnfc->fs.ring_cookie))
return -EFAULT;
if (ethcmd == ETHTOOL_GRXCLSRLALL) {
if (put_user(rule_cnt, &rxnfc->rule_cnt))
return -EFAULT;
} else if (copy_in_user(&rxnfc->rule_cnt,
&compat_rxnfc->rule_cnt,
sizeof(rxnfc->rule_cnt)))
return -EFAULT;
}