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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: 88db6d1e4f ("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>
This commit is contained in:
Michal Kubecek 2020-12-08 23:13:51 +01:00 committed by Jakub Kicinski
parent a379b01cd4
commit a770bf5156
1 changed files with 2 additions and 0 deletions
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2
net/ethtool/bitset.c
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@ -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)