| Message ID | 20210211212107.662291-1-arjunroy.kdev@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive. | expand |
On Thu, 11 Feb 2021 13:21:07 -0800 Arjun Roy wrote: > + if (unlikely(len > sizeof(zc))) { > + err = check_zeroed_user(optval + sizeof(zc), > + len - sizeof(zc)); > + if (err < 1) > + return err == 0 ? -EINVAL : err; nit: return err ? : -EINVAL; > len = sizeof(zc); > if (put_user(len, optlen)) > return -EFAULT; > } > if (copy_from_user(&zc, optval, len)) > return -EFAULT; > + if (zc.reserved) > + return -EINVAL; > + if (zc.msg_flags & ~(TCP_VALID_ZC_MSG_FLAGS)) nit: parens unnecessary But neither is a big deal: Acked-by: Jakub Kicinski <kuba@kernel.org>
Hello: This patch was applied to netdev/net-next.git (refs/heads/master): On Thu, 11 Feb 2021 13:21:07 -0800 you wrote: > From: Arjun Roy <arjunroy@google.com> > > Explicitly define reserved field and require it and any subsequent > fields to be zero-valued for now. Additionally, limit the valid CMSG > flags that tcp_zerocopy_receive accepts. > > Fixes: 7eeba1706eba ("tcp: Add receive timestamp support for receive zerocopy.") > Signed-off-by: Arjun Roy <arjunroy@google.com> > Signed-off-by: Eric Dumazet <edumazet@google.com> > Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> > Suggested-by: David Ahern <dsahern@gmail.com> > Suggested-by: Leon Romanovsky <leon@kernel.org> > Suggested-by: Jakub Kicinski <kuba@kernel.org> > > [...] Here is the summary with links: - [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive. https://git.kernel.org/netdev/net-next/c/3c5a2fd042d0 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
Hi Arjun,
url: https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537
base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520
config: x86_64-randconfig-m001-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
smatch warnings:
net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len'
vim +/len +4158 net/ipv4/tcp.c
3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3896 static int do_tcp_getsockopt(struct sock *sk, int level,
3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3897 int optname, char __user *optval, int __user *optlen)
^1da177e4c3f41 Linus Torvalds 2005-04-16 3898 {
295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09 3899 struct inet_connection_sock *icsk = inet_csk(sk);
^1da177e4c3f41 Linus Torvalds 2005-04-16 3900 struct tcp_sock *tp = tcp_sk(sk);
6fa251663069e0 Nikolay Borisov 2016-02-03 3901 struct net *net = sock_net(sk);
^1da177e4c3f41 Linus Torvalds 2005-04-16 3902 int val, len;
"len" is int.
[ snip ]
05255b823a6173 Eric Dumazet 2018-04-27 4146 #ifdef CONFIG_MMU
05255b823a6173 Eric Dumazet 2018-04-27 4147 case TCP_ZEROCOPY_RECEIVE: {
7eeba1706eba6d Arjun Roy 2021-01-20 4148 struct scm_timestamping_internal tss;
e0fecb289ad3fd Arjun Roy 2020-12-10 4149 struct tcp_zerocopy_receive zc = {};
05255b823a6173 Eric Dumazet 2018-04-27 4150 int err;
05255b823a6173 Eric Dumazet 2018-04-27 4151
05255b823a6173 Eric Dumazet 2018-04-27 4152 if (get_user(len, optlen))
05255b823a6173 Eric Dumazet 2018-04-27 4153 return -EFAULT;
c8856c05145490 Arjun Roy 2020-02-14 4154 if (len < offsetofend(struct tcp_zerocopy_receive, length))
05255b823a6173 Eric Dumazet 2018-04-27 4155 return -EINVAL;
The problem is that negative values of "len" are type promoted to high
positive values. So the fix is to write this as:
if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length))
return -EINVAL;
110912bdf28392 Arjun Roy 2021-02-11 4156 if (unlikely(len > sizeof(zc))) {
110912bdf28392 Arjun Roy 2021-02-11 4157 err = check_zeroed_user(optval + sizeof(zc),
110912bdf28392 Arjun Roy 2021-02-11 @4158 len - sizeof(zc));
^^^^^^^^^^^^^^^^
Potentially "len - a negative value".
110912bdf28392 Arjun Roy 2021-02-11 4159 if (err < 1)
110912bdf28392 Arjun Roy 2021-02-11 4160 return err == 0 ? -EINVAL : err;
c8856c05145490 Arjun Roy 2020-02-14 4161 len = sizeof(zc);
0b7f41f68710cc Arjun Roy 2020-02-25 4162 if (put_user(len, optlen))
0b7f41f68710cc Arjun Roy 2020-02-25 4163 return -EFAULT;
0b7f41f68710cc Arjun Roy 2020-02-25 4164 }
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
On 2/15/21 5:03 AM, Dan Carpenter wrote: > Hi Arjun, > > url: https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537 > base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520 > config: x86_64-randconfig-m001-20210209 (attached as .config) > compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp@intel.com> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > smatch warnings: > net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len' > > vim +/len +4158 net/ipv4/tcp.c > > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3896 static int do_tcp_getsockopt(struct sock *sk, int level, > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3897 int optname, char __user *optval, int __user *optlen) > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3898 { > 295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09 3899 struct inet_connection_sock *icsk = inet_csk(sk); > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3900 struct tcp_sock *tp = tcp_sk(sk); > 6fa251663069e0 Nikolay Borisov 2016-02-03 3901 struct net *net = sock_net(sk); > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3902 int val, len; > > "len" is int. > > [ snip ] > 05255b823a6173 Eric Dumazet 2018-04-27 4146 #ifdef CONFIG_MMU > 05255b823a6173 Eric Dumazet 2018-04-27 4147 case TCP_ZEROCOPY_RECEIVE: { > 7eeba1706eba6d Arjun Roy 2021-01-20 4148 struct scm_timestamping_internal tss; > e0fecb289ad3fd Arjun Roy 2020-12-10 4149 struct tcp_zerocopy_receive zc = {}; > 05255b823a6173 Eric Dumazet 2018-04-27 4150 int err; > 05255b823a6173 Eric Dumazet 2018-04-27 4151 > 05255b823a6173 Eric Dumazet 2018-04-27 4152 if (get_user(len, optlen)) > 05255b823a6173 Eric Dumazet 2018-04-27 4153 return -EFAULT; > c8856c05145490 Arjun Roy 2020-02-14 4154 if (len < offsetofend(struct tcp_zerocopy_receive, length)) > 05255b823a6173 Eric Dumazet 2018-04-27 4155 return -EINVAL; > > > The problem is that negative values of "len" are type promoted to high > positive values. So the fix is to write this as: > > if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length)) > return -EINVAL; > > 110912bdf28392 Arjun Roy 2021-02-11 4156 if (unlikely(len > sizeof(zc))) { > 110912bdf28392 Arjun Roy 2021-02-11 4157 err = check_zeroed_user(optval + sizeof(zc), > 110912bdf28392 Arjun Roy 2021-02-11 @4158 len - sizeof(zc)); > ^^^^^^^^^^^^^^^^ > Potentially "len - a negative value". > > get_user(len, optlen) is called multiple times in that function. len < 0 was checked after the first one at the top. Also, maybe I am missing something here, but offsetofend can not return a negative value, so this checks catches len < 0 as well: if (len < offsetofend(struct tcp_zerocopy_receive, length)) return -EINVAL;
On Mon, Feb 15, 2021 at 08:04:11AM -0700, David Ahern wrote: > On 2/15/21 5:03 AM, Dan Carpenter wrote: > > Hi Arjun, > > > > url: https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537 > > base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520 > > config: x86_64-randconfig-m001-20210209 (attached as .config) > > compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 > > > > If you fix the issue, kindly add following tag as appropriate > > Reported-by: kernel test robot <lkp@intel.com> > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > > > smatch warnings: > > net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len' > > > > vim +/len +4158 net/ipv4/tcp.c > > > > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3896 static int do_tcp_getsockopt(struct sock *sk, int level, > > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3897 int optname, char __user *optval, int __user *optlen) > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3898 { > > 295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09 3899 struct inet_connection_sock *icsk = inet_csk(sk); > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3900 struct tcp_sock *tp = tcp_sk(sk); > > 6fa251663069e0 Nikolay Borisov 2016-02-03 3901 struct net *net = sock_net(sk); > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3902 int val, len; > > > > "len" is int. > > > > [ snip ] > > 05255b823a6173 Eric Dumazet 2018-04-27 4146 #ifdef CONFIG_MMU > > 05255b823a6173 Eric Dumazet 2018-04-27 4147 case TCP_ZEROCOPY_RECEIVE: { > > 7eeba1706eba6d Arjun Roy 2021-01-20 4148 struct scm_timestamping_internal tss; > > e0fecb289ad3fd Arjun Roy 2020-12-10 4149 struct tcp_zerocopy_receive zc = {}; > > 05255b823a6173 Eric Dumazet 2018-04-27 4150 int err; > > 05255b823a6173 Eric Dumazet 2018-04-27 4151 > > 05255b823a6173 Eric Dumazet 2018-04-27 4152 if (get_user(len, optlen)) > > 05255b823a6173 Eric Dumazet 2018-04-27 4153 return -EFAULT; > > c8856c05145490 Arjun Roy 2020-02-14 4154 if (len < offsetofend(struct tcp_zerocopy_receive, length)) > > 05255b823a6173 Eric Dumazet 2018-04-27 4155 return -EINVAL; > > > > > > The problem is that negative values of "len" are type promoted to high > > positive values. So the fix is to write this as: > > > > if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length)) > > return -EINVAL; > > > > 110912bdf28392 Arjun Roy 2021-02-11 4156 if (unlikely(len > sizeof(zc))) { > > 110912bdf28392 Arjun Roy 2021-02-11 4157 err = check_zeroed_user(optval + sizeof(zc), > > 110912bdf28392 Arjun Roy 2021-02-11 @4158 len - sizeof(zc)); > > ^^^^^^^^^^^^^^^^ > > Potentially "len - a negative value". > > > > > > get_user(len, optlen) is called multiple times in that function. len < 0 > was checked after the first one at the top. > What you're describing is a "Double Fetch" bug, where the attack is we get some data from the user, and we verify it, then we get it from the user a second time and trust it. The problem is that the user modifies it between the first and second get_user() call so it ends up being a security vulnerability. But I'm glad you pointed out the first get_user() because it has an ancient, harmless pre git bug in it. net/ipv4/tcp.c 3888 static int do_tcp_getsockopt(struct sock *sk, int level, 3889 int optname, char __user *optval, int __user *optlen) 3890 { 3891 struct inet_connection_sock *icsk = inet_csk(sk); 3892 struct tcp_sock *tp = tcp_sk(sk); 3893 struct net *net = sock_net(sk); 3894 int val, len; 3895 3896 if (get_user(len, optlen)) 3897 return -EFAULT; 3898 3899 len = min_t(unsigned int, len, sizeof(int)); 3900 3901 if (len < 0) ^^^^^^^ This is impossible. "len" has to be in the 0-4 range because of the min_t() assignment. It's harmless though and the condition should just be removed. 3902 return -EINVAL; 3903 3904 switch (optname) { 3905 case TCP_MAXSEG: Anyway, I will create a new Smatch warning for this situation. > Also, maybe I am missing something here, but offsetofend can not return > a negative value, so this checks catches len < 0 as well: > > if (len < offsetofend(struct tcp_zerocopy_receive, length)) > return -EINVAL; > offsetofend is (unsigned long)12. If we compare a negative integer with (unsigned long)12 then negative number is type promoted to a high positive value. if (-1 < (usigned long)12) printf("dan is wrong\n"); regards, dan carpenter
On Mon, Feb 15, 2021 at 8:02 AM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > On Mon, Feb 15, 2021 at 08:04:11AM -0700, David Ahern wrote: > > On 2/15/21 5:03 AM, Dan Carpenter wrote: > > > Hi Arjun, > > > > > > url: https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537 > > > base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520 > > > config: x86_64-randconfig-m001-20210209 (attached as .config) > > > compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 > > > > > > If you fix the issue, kindly add following tag as appropriate > > > Reported-by: kernel test robot <lkp@intel.com> > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > > > > > smatch warnings: > > > net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len' > > > > > > vim +/len +4158 net/ipv4/tcp.c > > > > > > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3896 static int do_tcp_getsockopt(struct sock *sk, int level, > > > 3fdadf7d27e3fb Dmitry Mishin 2006-03-20 3897 int optname, char __user *optval, int __user *optlen) > > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3898 { > > > 295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09 3899 struct inet_connection_sock *icsk = inet_csk(sk); > > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3900 struct tcp_sock *tp = tcp_sk(sk); > > > 6fa251663069e0 Nikolay Borisov 2016-02-03 3901 struct net *net = sock_net(sk); > > > ^1da177e4c3f41 Linus Torvalds 2005-04-16 3902 int val, len; > > > > > > "len" is int. > > > > > > [ snip ] > > > 05255b823a6173 Eric Dumazet 2018-04-27 4146 #ifdef CONFIG_MMU > > > 05255b823a6173 Eric Dumazet 2018-04-27 4147 case TCP_ZEROCOPY_RECEIVE: { > > > 7eeba1706eba6d Arjun Roy 2021-01-20 4148 struct scm_timestamping_internal tss; > > > e0fecb289ad3fd Arjun Roy 2020-12-10 4149 struct tcp_zerocopy_receive zc = {}; > > > 05255b823a6173 Eric Dumazet 2018-04-27 4150 int err; > > > 05255b823a6173 Eric Dumazet 2018-04-27 4151 > > > 05255b823a6173 Eric Dumazet 2018-04-27 4152 if (get_user(len, optlen)) > > > 05255b823a6173 Eric Dumazet 2018-04-27 4153 return -EFAULT; > > > c8856c05145490 Arjun Roy 2020-02-14 4154 if (len < offsetofend(struct tcp_zerocopy_receive, length)) > > > 05255b823a6173 Eric Dumazet 2018-04-27 4155 return -EINVAL; > > > > > > > > > The problem is that negative values of "len" are type promoted to high > > > positive values. So the fix is to write this as: > > > > > > if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length)) > > > return -EINVAL; > > > > > > 110912bdf28392 Arjun Roy 2021-02-11 4156 if (unlikely(len > sizeof(zc))) { > > > 110912bdf28392 Arjun Roy 2021-02-11 4157 err = check_zeroed_user(optval + sizeof(zc), > > > 110912bdf28392 Arjun Roy 2021-02-11 @4158 len - sizeof(zc)); > > > ^^^^^^^^^^^^^^^^ > > > Potentially "len - a negative value". > > > > > > > > > > get_user(len, optlen) is called multiple times in that function. len < 0 > > was checked after the first one at the top. > > > > What you're describing is a "Double Fetch" bug, where the attack is we > get some data from the user, and we verify it, then we get it from the > user a second time and trust it. The problem is that the user modifies > it between the first and second get_user() call so it ends up being a > security vulnerability. > > But I'm glad you pointed out the first get_user() because it has an > ancient, harmless pre git bug in it. > > net/ipv4/tcp.c > 3888 static int do_tcp_getsockopt(struct sock *sk, int level, > 3889 int optname, char __user *optval, int __user *optlen) > 3890 { > 3891 struct inet_connection_sock *icsk = inet_csk(sk); > 3892 struct tcp_sock *tp = tcp_sk(sk); > 3893 struct net *net = sock_net(sk); > 3894 int val, len; > 3895 > 3896 if (get_user(len, optlen)) > 3897 return -EFAULT; > 3898 > 3899 len = min_t(unsigned int, len, sizeof(int)); > 3900 > 3901 if (len < 0) > ^^^^^^^ > This is impossible. "len" has to be in the 0-4 range because of the > min_t() assignment. It's harmless though and the condition should just > be removed. > > 3902 return -EINVAL; > 3903 > 3904 switch (optname) { > 3905 case TCP_MAXSEG: > > Anyway, I will create a new Smatch warning for this situation. > > > Also, maybe I am missing something here, but offsetofend can not return > > a negative value, so this checks catches len < 0 as well: > > > > if (len < offsetofend(struct tcp_zerocopy_receive, length)) > > return -EINVAL; > > > > offsetofend is (unsigned long)12. If we compare a negative integer with > (unsigned long)12 then negative number is type promoted to a high > positive value. > > if (-1 < (usigned long)12) > printf("dan is wrong\n"); > > regards, > dan carpenter > > Thank you for the catch. I will send out a fix momentarily. Actually, now I'm curious - why does do_tcp_getsockopt get called so many times, per getsockopt target - rather than just using the originally read value? -Arjun
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 42fc5a640df4..8fc09e8638b3 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -357,6 +357,6 @@ struct tcp_zerocopy_receive { __u64 msg_control; /* ancillary data */ __u64 msg_controllen; __u32 msg_flags; - /* __u32 hole; Next we must add >1 u32 otherwise length checks fail. */ + __u32 reserved; /* set to 0 for now */ }; #endif /* _UAPI_LINUX_TCP_H */ diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index e1a17c6b473c..9896ca10bb34 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2030,6 +2030,7 @@ static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma, err); } +#define TCP_VALID_ZC_MSG_FLAGS (TCP_CMSG_TS) static void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk, struct scm_timestamping_internal *tss); static void tcp_zc_finalize_rx_tstamp(struct sock *sk, @@ -4152,13 +4153,21 @@ static int do_tcp_getsockopt(struct sock *sk, int level, return -EFAULT; if (len < offsetofend(struct tcp_zerocopy_receive, length)) return -EINVAL; - if (len > sizeof(zc)) { + if (unlikely(len > sizeof(zc))) { + err = check_zeroed_user(optval + sizeof(zc), + len - sizeof(zc)); + if (err < 1) + return err == 0 ? -EINVAL : err; len = sizeof(zc); if (put_user(len, optlen)) return -EFAULT; } if (copy_from_user(&zc, optval, len)) return -EFAULT; + if (zc.reserved) + return -EINVAL; + if (zc.msg_flags & ~(TCP_VALID_ZC_MSG_FLAGS)) + return -EINVAL; lock_sock(sk); err = tcp_zerocopy_receive(sk, &zc, &tss); release_sock(sk);