| Message ID | 20180804235544.10347-1-dima@arista.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | netlink: Don't shift on 64 for ngroups | expand |
From: Dmitry Safonov <dima@arista.com> Date: Sun, 5 Aug 2018 00:55:44 +0100 > @@ -1011,8 +1011,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, > > if (nlk->ngroups == 0) > groups = 0; > - else > - groups &= (1ULL << nlk->ngroups) - 1; > + else if (nlk->ngroups < sizeof(long unsigned int)) > + groups &= (1UL << nlk->ngroups) - 1; Sizeof is in bytes, you want to compare against bits.
On Sat, 2018-08-04 at 17:08 -0700, David Miller wrote: > From: Dmitry Safonov <dima@arista.com> > Date: Sun, 5 Aug 2018 00:55:44 +0100 > > > @@ -1011,8 +1011,8 @@ static int netlink_bind(struct socket *sock, > struct sockaddr *addr, > > > > if (nlk->ngroups == 0) > > groups = 0; > > - else > > - groups &= (1ULL << nlk->ngroups) - 1; > > + else if (nlk->ngroups < sizeof(long unsigned int)) > > + groups &= (1UL << nlk->ngroups) - 1; > > Sizeof is in bytes, you want to compare against bits. I'm too bad. Drop this version, please. I've resent v2.
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 7d860a22e5fb..e44edadfad20 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1011,8 +1011,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, if (nlk->ngroups == 0) groups = 0; - else - groups &= (1ULL << nlk->ngroups) - 1; + else if (nlk->ngroups < sizeof(long unsigned int)) + groups &= (1UL << nlk->ngroups) - 1; bound = nlk->bound; if (bound) {
It's legal to have 64 groups for netlink_sock. As user-supplied nladdr->nl_groups is __u32, it's possible to subscribe only to first 32 groups. The check for correctness of .bind() userspace supplied parameter is done by applying mask made from ngroups shift. Which broke Android as they have 64 groups and the shift for mask resulted in an overflow. Fixes: 61f4b23769f0 ("netlink: Don't shift with UB on nlk->ngroups") Cc: "David S. Miller" <davem@davemloft.net> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: netdev@vger.kernel.org Cc: stable@vger.kernel.org Reported-and-Tested-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> --- net/netlink/af_netlink.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)