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authorFlorian Westphal <fw@strlen.de>2020-08-13 10:46:11 +0300
committerPablo Neira Ayuso <pablo@netfilter.org>2020-08-14 12:59:08 +0300
commit5c04da55c754c44937b3d19c6522f9023fd5c5d5 (patch)
treed578d1669d5f5b64c77254c0272f3191e74f3cff /net/bridge/netfilter
parentd8bb9abe21071c64d077f9db3b403823a389464f (diff)
downloadlinux-5c04da55c754c44937b3d19c6522f9023fd5c5d5.tar.xz
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>
Diffstat (limited to 'net/bridge/netfilter')
-rw-r--r--net/bridge/netfilter/ebtables.c4
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;