This is a note to let you know that I've just added the patch titled net: sctp, forbid negative length to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-sctp-forbid-negative-length.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Nov 10 16:42:45 CET 2016 From: Jiri Slaby <jslaby@xxxxxxx> Date: Fri, 21 Oct 2016 14:13:24 +0200 Subject: net: sctp, forbid negative length From: Jiri Slaby <jslaby@xxxxxxx> [ 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@xxxxxxx> Cc: Vlad Yasevich <vyasevich@xxxxxxxxx> Cc: Neil Horman <nhorman@xxxxxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: linux-sctp@xxxxxxxxxxxxxxx Cc: netdev@xxxxxxxxxxxxxxx Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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) { Patches currently in stable-queue which might be from jslaby@xxxxxxx are queue-4.4/net-sctp-forbid-negative-length.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html