* [PATCH 4.4 23/34] net: sctp, forbid negative length
[not found] <20161113112400.008903838@linuxfoundation.org>
@ 2016-11-13 11:24 ` Greg Kroah-Hartman
0 siblings, 0 replies; only message in thread
From: Greg Kroah-Hartman @ 2016-11-13 11:24 UTC (permalink / raw)
To: linux-kernel
Cc: Greg Kroah-Hartman, stable, Jiri Slaby, Vlad Yasevich,
Neil Horman, David S. Miller, linux-sctp, netdev
4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Slaby <jslaby@suse•cz>
[ Upstream commit a4b8e71b05c27bae6bad3bdecddbc6b68a3ad8cf ]
Most of getsockopt handlers in net/sctp/socket.c check len against
sizeof some structure like:
if (len < sizeof(int))
return -EINVAL;
On the first look, the check seems to be correct. But since len is int
and sizeof returns size_t, int gets promoted to unsigned size_t too. So
the test returns false for negative lengths. Yes, (-1 < sizeof(long)) is
false.
Fix this in sctp by explicitly checking len < 0 before any getsockopt
handler is called.
Note that sctp_getsockopt_events already handled the negative case.
Since we added the < 0 check elsewhere, this one can be removed.
If not checked, this is the result:
UBSAN: Undefined behaviour in ../mm/page_alloc.c:2722:19
shift exponent 52 is too large for 32-bit type 'int'
CPU: 1 PID: 24535 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
0000000000000000 ffff88006d99f2a8 ffffffffb2f7bdea 0000000041b58ab3
ffffffffb4363c14 ffffffffb2f7bcde ffff88006d99f2d0 ffff88006d99f270
0000000000000000 0000000000000000 0000000000000034 ffffffffb5096422
Call Trace:
[<ffffffffb3051498>] ? __ubsan_handle_shift_out_of_bounds+0x29c/0x300
...
[<ffffffffb273f0e4>] ? kmalloc_order+0x24/0x90
[<ffffffffb27416a4>] ? kmalloc_order_trace+0x24/0x220
[<ffffffffb2819a30>] ? __kmalloc+0x330/0x540
[<ffffffffc18c25f4>] ? sctp_getsockopt_local_addrs+0x174/0xca0 [sctp]
[<ffffffffc18d2bcd>] ? sctp_getsockopt+0x10d/0x1b0 [sctp]
[<ffffffffb37c1219>] ? sock_common_getsockopt+0xb9/0x150
[<ffffffffb37be2f5>] ? SyS_getsockopt+0x1a5/0x270
Signed-off-by: Jiri Slaby <jslaby@suse•cz>
Cc: Vlad Yasevich <vyasevich@gmail•com>
Cc: Neil Horman <nhorman@tuxdriver•com>
Cc: "David S. Miller" <davem@davemloft•net>
Cc: linux-sctp@vger•kernel.org
Cc: netdev@vger•kernel.org
Acked-by: Neil Horman <nhorman@tuxdriver•com>
Signed-off-by: David S. Miller <davem@davemloft•net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation•org>
---
net/sctp/socket.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4371,7 +4371,7 @@ static int sctp_getsockopt_disable_fragm
static int sctp_getsockopt_events(struct sock *sk, int len, char __user *optval,
int __user *optlen)
{
- if (len <= 0)
+ if (len == 0)
return -EINVAL;
if (len > sizeof(struct sctp_event_subscribe))
len = sizeof(struct sctp_event_subscribe);
@@ -5972,6 +5972,9 @@ static int sctp_getsockopt(struct sock *
if (get_user(len, optlen))
return -EFAULT;
+ if (len < 0)
+ return -EINVAL;
+
lock_sock(sk);
switch (optname) {
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