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| author | Linus Lüssing <linus.luessing@c0d3.blue> | 2015-08-13 05:54:07 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-08-13 17:08:39 -0700 |
| commit | a516993f0ac1694673412eb2d16a091eafa77d2a (patch) | |
| tree | 43e65ff360cc79cff96dc8c44f161fb0ad41b9c9 /net/ipv6 | |
| parent | 5b3e2e14eaa2a98232a4f292341fb88438685734 (diff) | |
| download | linux-a516993f0ac1694673412eb2d16a091eafa77d2a.tar.bz2 | |
net: fix wrong skb_get() usage / crash in IGMP/MLD parsing code
The recent refactoring of the IGMP and MLD parsing code into
ipv6_mc_check_mld() / ip_mc_check_igmp() introduced a potential crash /
BUG() invocation for bridges:
I wrongly assumed that skb_get() could be used as a simple reference
counter for an skb which is not the case. skb_get() bears additional
semantics, a user count. This leads to a BUG() invocation in
pskb_expand_head() / kernel panic if pskb_may_pull() is called on an skb
with a user count greater than one - unfortunately the refactoring did
just that.
Fixing this by removing the skb_get() call and changing the API: The
caller of ipv6_mc_check_mld() / ip_mc_check_igmp() now needs to
additionally check whether the returned skb_trimmed is a clone.
Fixes: 9afd85c9e455 ("net: Export IGMP/MLD message validation code")
Reported-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
| -rw-r--r-- | net/ipv6/mcast_snoop.c | 33 |
1 files changed, 18 insertions, 15 deletions
diff --git a/net/ipv6/mcast_snoop.c b/net/ipv6/mcast_snoop.c index df8afe5ab31e..9405b04eecc6 100644 --- a/net/ipv6/mcast_snoop.c +++ b/net/ipv6/mcast_snoop.c @@ -143,34 +143,36 @@ static int __ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff *skb_chk = NULL; unsigned int transport_len; unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg); - int ret; + int ret = -EINVAL; transport_len = ntohs(ipv6_hdr(skb)->payload_len); transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr); - skb_get(skb); skb_chk = skb_checksum_trimmed(skb, transport_len, ipv6_mc_validate_checksum); if (!skb_chk) - return -EINVAL; + goto err; - if (!pskb_may_pull(skb_chk, len)) { - kfree_skb(skb_chk); - return -EINVAL; - } + if (!pskb_may_pull(skb_chk, len)) + goto err; ret = ipv6_mc_check_mld_msg(skb_chk); - if (ret) { - kfree_skb(skb_chk); - return ret; - } + if (ret) + goto err; if (skb_trimmed) *skb_trimmed = skb_chk; - else + /* free now unneeded clone */ + else if (skb_chk != skb) kfree_skb(skb_chk); - return 0; + ret = 0; + +err: + if (ret && skb_chk && skb_chk != skb) + kfree_skb(skb_chk); + + return ret; } /** @@ -179,7 +181,7 @@ static int __ipv6_mc_check_mld(struct sk_buff *skb, * @skb_trimmed: to store an skb pointer trimmed to IPv6 packet tail (optional) * * Checks whether an IPv6 packet is a valid MLD packet. If so sets - * skb network and transport headers accordingly and returns zero. + * skb transport header accordingly and returns zero. * * -EINVAL: A broken packet was detected, i.e. it violates some internet * standard @@ -194,7 +196,8 @@ static int __ipv6_mc_check_mld(struct sk_buff *skb, * to leave the original skb and its full frame unchanged (which might be * desirable for layer 2 frame jugglers). * - * The caller needs to release a reference count from any returned skb_trimmed. + * Caller needs to set the skb network header and free any returned skb if it + * differs from the provided skb. */ int ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed) { |