diff options
author | Florian Westphal <fw@strlen.de> | 2020-08-13 09:46:11 +0200 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2020-08-14 11:59:08 +0200 |
commit | 5c04da55c754c44937b3d19c6522f9023fd5c5d5 (patch) | |
tree | d578d1669d5f5b64c77254c0272f3191e74f3cff | |
parent | d8bb9abe21071c64d077f9db3b403823a389464f (diff) | |
download | linux-5c04da55c754c44937b3d19c6522f9023fd5c5d5.tar.bz2 |
netfilter: ebtables: reject bogus getopt len value
syzkaller reports splat:
------------[ cut here ]------------
Buffer overflow detected (80 < 137)!
Call Trace:
do_ebt_get_ctl+0x2b4/0x790 net/bridge/netfilter/ebtables.c:2317
nf_getsockopt+0x72/0xd0 net/netfilter/nf_sockopt.c:116
ip_getsockopt net/ipv4/ip_sockglue.c:1778 [inline]
caused by a copy-to-user with a too-large "*len" value.
This adds a argument check on *len just like in the non-compat version
of the handler.
Before the "Fixes" commit, the reproducer fails with -EINVAL as
expected:
1. core calls the "compat" getsockopt version
2. compat getsockopt version detects the *len value is possibly
in 64-bit layout (*len != compat_len)
3. compat getsockopt version delegates everything to native getsockopt
version
4. native getsockopt rejects invalid *len
-> compat handler only sees len == sizeof(compat_struct) for GET_ENTRIES.
After the refactor, event sequence is:
1. getsockopt calls "compat" version (len != native_len)
2. compat version attempts to copy *len bytes, where *len is random
value from userspace
Fixes: fc66de8e16ec ("netfilter/ebtables: clean up compat {get, set}sockopt handling")
Reported-by: syzbot+5accb5c62faa1d346480@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
-rw-r--r-- | net/bridge/netfilter/ebtables.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c index 1641f414d1ba..ebe33b60efd6 100644 --- a/net/bridge/netfilter/ebtables.c +++ b/net/bridge/netfilter/ebtables.c @@ -2238,6 +2238,10 @@ static int compat_do_ebt_get_ctl(struct sock *sk, int cmd, struct ebt_table *t; struct net *net = sock_net(sk); + if ((cmd == EBT_SO_GET_INFO || cmd == EBT_SO_GET_INIT_INFO) && + *len != sizeof(struct compat_ebt_replace)) + return -EINVAL; + if (copy_from_user(&tmp, user, sizeof(tmp))) return -EFAULT; |