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Date: Tue, 3 Mar 2020 18:43:24 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Christophe Leroy <christophe.leroy@....fr>, Richard Guy Briggs <rgb@...hat.com>, "Erhard F." <erhard_f@...lbox.org>, Nikolay Aleksandrov <nikolay@...ulusnetworks.com>, "David S. Miller" <davem@...emloft.net> Subject: [PATCH 5.4 106/152] net: netlink: cap max groups which will be considered in netlink_bind() From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com> commit 3a20773beeeeadec41477a5ba872175b778ff752 upstream. Since nl_groups is a u32 we can't bind more groups via ->bind (netlink_bind) call, but netlink has supported more groups via setsockopt() for a long time and thus nlk->ngroups could be over 32. Recently I added support for per-vlan notifications and increased the groups to 33 for NETLINK_ROUTE which exposed an old bug in the netlink_bind() code causing out-of-bounds access on archs where unsigned long is 32 bits via test_bit() on a local variable. Fix this by capping the maximum groups in netlink_bind() to BITS_PER_TYPE(u32), effectively capping them at 32 which is the minimum of allocated groups and the maximum groups which can be bound via netlink_bind(). CC: Christophe Leroy <christophe.leroy@....fr> CC: Richard Guy Briggs <rgb@...hat.com> Fixes: 4f520900522f ("netlink: have netlink per-protocol bind function return an error code.") Reported-by: Erhard F. <erhard_f@...lbox.org> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- net/netlink/af_netlink.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1014,7 +1014,8 @@ static int netlink_bind(struct socket *s if (nlk->netlink_bind && groups) { int group; - for (group = 0; group < nlk->ngroups; group++) { + /* nl_groups is a u32, so cap the maximum groups we can bind */ + for (group = 0; group < BITS_PER_TYPE(u32); group++) { if (!test_bit(group, &groups)) continue; err = nlk->netlink_bind(net, group + 1); @@ -1033,7 +1034,7 @@ static int netlink_bind(struct socket *s netlink_insert(sk, nladdr->nl_pid) : netlink_autobind(sock); if (err) { - netlink_undo_bind(nlk->ngroups, groups, sk); + netlink_undo_bind(BITS_PER_TYPE(u32), groups, sk); goto unlock; } }
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