Commit a770bf51 authored Dec 08, 2020 by Michal Kubecek Committed by Jakub Kicinski Dec 09, 2020

ethtool: fix stack overflow in ethnl_parse_bitset()

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: 88db6d1e ("ethtool: add ethnl_parse_bitset() helper")
Reported-by: <syzbot+9d39fa49d4df294aab93@syzkaller.appspotmail.com>
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Link: https://lore.kernel.org/r/3487ee3a98e14cd526f55b6caaa959d2dcbcad9f.1607465316.git.mkubecek@suse.cz

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent a379b01c

net/ethtool/bitset.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -628,6 +628,8 @@ 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)