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authorMichal Kubecek <mkubecek@suse.cz>2020-02-24 20:42:12 +0100
committerDavid S. Miller <davem@davemloft.net>2020-02-26 11:27:31 -0800
commite34f1753eebc428c312527662eb1b529cf260240 (patch)
tree667163607addcc7d8c0ab4af5ab726fdfa71bcf0 /net
parent6e11d1578fba8d09d03a286740ffcf336d53928c (diff)
ethtool: limit bitset size
Syzbot reported that ethnl_compact_sanity_checks() can be tricked into reading past the end of ETHTOOL_A_BITSET_VALUE and ETHTOOL_A_BITSET_MASK attributes and even the message by passing a value between (u32)(-31) and (u32)(-1) as ETHTOOL_A_BITSET_SIZE. The problem is that DIV_ROUND_UP(attr_nbits, 32) is 0 for such values so that zero length ETHTOOL_A_BITSET_VALUE will pass the length check but ethnl_bitmap32_not_zero() check would try to access up to 512 MB of attribute "payload". Prevent this overflow byt limiting the bitset size. Technically, compact bitset format would allow bitset sizes up to almost 2^18 (so that the nest size does not exceed U16_MAX) but bitsets used by ethtool are much shorter. S16_MAX, the largest value which can be directly used as an upper limit in policy, should be a reasonable compromise. Fixes: 10b518d4e6dd ("ethtool: netlink bitset handling") Reported-by: syzbot+7fd4ed5b4234ab1fdccd@syzkaller.appspotmail.com Reported-by: syzbot+709b7a64d57978247e44@syzkaller.appspotmail.com Reported-by: syzbot+983cb8fb2d17a7af549d@syzkaller.appspotmail.com Signed-off-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ethtool/bitset.c3
-rw-r--r--net/ethtool/bitset.h2
2 files changed, 4 insertions, 1 deletions
diff --git a/net/ethtool/bitset.c b/net/ethtool/bitset.c
index 8977fe1f3946..ef9197541cb3 100644
--- a/net/ethtool/bitset.c
+++ b/net/ethtool/bitset.c
@@ -305,7 +305,8 @@ nla_put_failure:
static const struct nla_policy bitset_policy[ETHTOOL_A_BITSET_MAX + 1] = {
[ETHTOOL_A_BITSET_UNSPEC] = { .type = NLA_REJECT },
[ETHTOOL_A_BITSET_NOMASK] = { .type = NLA_FLAG },
- [ETHTOOL_A_BITSET_SIZE] = { .type = NLA_U32 },
+ [ETHTOOL_A_BITSET_SIZE] = NLA_POLICY_MAX(NLA_U32,
+ ETHNL_MAX_BITSET_SIZE),
[ETHTOOL_A_BITSET_BITS] = { .type = NLA_NESTED },
[ETHTOOL_A_BITSET_VALUE] = { .type = NLA_BINARY },
[ETHTOOL_A_BITSET_MASK] = { .type = NLA_BINARY },
diff --git a/net/ethtool/bitset.h b/net/ethtool/bitset.h
index b8247e34109d..b849f9d19676 100644
--- a/net/ethtool/bitset.h
+++ b/net/ethtool/bitset.h
@@ -3,6 +3,8 @@
#ifndef _NET_ETHTOOL_BITSET_H
#define _NET_ETHTOOL_BITSET_H
+#define ETHNL_MAX_BITSET_SIZE S16_MAX
+
typedef const char (*const ethnl_string_array_t)[ETH_GSTRING_LEN];
int ethnl_bitset_is_compact(const struct nlattr *bitset, bool *compact);