From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Arjun Roy arjunroy@google.com
commit 2107d45f17bedd7dbf4178462da0ac223835a2a7 upstream.
getsockopt(TCP_ZEROCOPY_RECEIVE) has a bug where we read a user-provided "len" field of type signed int, and then compare the value to the result of an "offsetofend" operation, which is unsigned.
Negative values provided by the user will be promoted to large positive numbers; thus checking that len < offsetofend() will return false when the intention was that it return true.
Note that while len is originally checked for negative values earlier on in do_tcp_getsockopt(), subsequent calls to get_user() re-read the value from userspace which may have changed in the meantime.
Therefore, re-add the check for negative values after the call to get_user in the handler code for TCP_ZEROCOPY_RECEIVE.
Fixes: c8856c051454 ("tcp-zerocopy: Return inq along with tcp receive zerocopy.") Reported-by: kernel test robot lkp@intel.com Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Arjun Roy arjunroy@google.com Link: https://lore.kernel.org/r/20210225232628.4033281-1-arjunroy.kdev@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4088,7 +4088,8 @@ static int do_tcp_getsockopt(struct sock
if (get_user(len, optlen)) return -EFAULT; - if (len < offsetofend(struct tcp_zerocopy_receive, length)) + if (len < 0 || + len < offsetofend(struct tcp_zerocopy_receive, length)) return -EINVAL; if (len > sizeof(zc)) { len = sizeof(zc);