From cda8b1cbecacacf4e378930dcf7ea787a6f6e2c1 Mon Sep 17 00:00:00 2001 From: Arjun Roy Date: Thu, 25 Feb 2021 15:26:28 -0800 Subject: [PATCH] tcp: Fix sign comparison bug in getsockopt(TCP_ZEROCOPY_RECEIVE) 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 Reported-by: Dan Carpenter Signed-off-by: Arjun Roy Link: https://lore.kernel.org/r/20210225232628.4033281-1-arjunroy.kdev@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 32545ecf2ab10..f3b6c8f53e07d 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4088,7 +4088,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level, 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);