From: Michal Kubecek Date: Tue, 8 Dec 2020 22:13:51 +0000 (+0100) Subject: ethtool: fix stack overflow in ethnl_parse_bitset() X-Git-Tag: v5.9.16~28 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8d50009dadaa7f4d179af59e9796628c7487cf8;p=thirdparty%2Fkernel%2Fstable.git ethtool: fix stack overflow in ethnl_parse_bitset() [ Upstream commit a770bf515613c6e12ae904c3593e26016de99448 ] Syzbot reported a stack overflow in bitmap_from_arr32() called from ethnl_parse_bitset() when bitset from netlink message is longer than target bitmap length. While ethnl_compact_sanity_checks() makes sure that trailing part is all zeros (i.e. the request does not try to touch bits kernel does not recognize), we also need to cap change_bits to nbits so that we don't try to write past the prepared bitmaps. Fixes: 88db6d1e4f62 ("ethtool: add ethnl_parse_bitset() helper") Reported-by: syzbot+9d39fa49d4df294aab93@syzkaller.appspotmail.com Signed-off-by: Michal Kubecek Link: https://lore.kernel.org/r/3487ee3a98e14cd526f55b6caaa959d2dcbcad9f.1607465316.git.mkubecek@suse.cz Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ethtool/bitset.c b/net/ethtool/bitset.c index dae7402eaca39..2851f25b0af41 100644 --- a/net/ethtool/bitset.c +++ b/net/ethtool/bitset.c @@ -630,6 +630,8 @@ int ethnl_parse_bitset(unsigned long *val, unsigned long *mask, return ret; change_bits = nla_get_u32(tb[ETHTOOL_A_BITSET_SIZE]); + if (change_bits > nbits) + change_bits = nbits; bitmap_from_arr32(val, nla_data(tb[ETHTOOL_A_BITSET_VALUE]), change_bits); if (change_bits < nbits)