Patch "sctp: do not leak kernel memory to user space" has been added to the 4.9-stable tree

Patch "sctp: do not leak kernel memory to user space" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    sctp: do not leak kernel memory to user space

to the 4.9-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:
     sctp-do-not-leak-kernel-memory-to-user-space.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Apr 11 10:26:56 CEST 2018
From: Eric Dumazet <edumazet@google.com>
Date: Sat, 7 Apr 2018 17:15:22 -0700
Subject: sctp: do not leak kernel memory to user space

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit 6780db244d6b1537d139dea0ec8aad10cf9e4adb ]

syzbot produced a nice report [1]

Issue here is that a recvmmsg() managed to leak 8 bytes of kernel memory
to user space, because sin_zero (padding field) was not properly cleared.

[1]
BUG: KMSAN: uninit-value in copy_to_user include/linux/uaccess.h:184 [inline]
BUG: KMSAN: uninit-value in move_addr_to_user+0x32e/0x530 net/socket.c:227
CPU: 1 PID: 3586 Comm: syzkaller481044 Not tainted 4.16.0+ #82
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 kmsan_internal_check_memory+0x164/0x1d0 mm/kmsan/kmsan.c:1176
 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199
 copy_to_user include/linux/uaccess.h:184 [inline]
 move_addr_to_user+0x32e/0x530 net/socket.c:227
 ___sys_recvmsg+0x4e2/0x810 net/socket.c:2211
 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313
 SYSC_recvmmsg+0x29b/0x3e0 net/socket.c:2394
 SyS_recvmmsg+0x76/0xa0 net/socket.c:2378
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x4401c9
RSP: 002b:00007ffc56f73098 EFLAGS: 00000217 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401c9
RDX: 0000000000000001 RSI: 0000000020003ac0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000020003bc0 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401af0
R13: 0000000000401b80 R14: 0000000000000000 R15: 0000000000000000

Local variable description: ----addr@___sys_recvmsg
Variable was created at:
 ___sys_recvmsg+0xd5/0x810 net/socket.c:2172
 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313

Bytes 8-15 of 16 are uninitialized

==================================================================
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3586 Comm: syzkaller481044 Tainted: G    B            4.16.0+ #82
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 panic+0x39d/0x940 kernel/panic.c:183
 kmsan_report+0x238/0x240 mm/kmsan/kmsan.c:1083
 kmsan_internal_check_memory+0x164/0x1d0 mm/kmsan/kmsan.c:1176
 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199
 copy_to_user include/linux/uaccess.h:184 [inline]
 move_addr_to_user+0x32e/0x530 net/socket.c:227
 ___sys_recvmsg+0x4e2/0x810 net/socket.c:2211
 __sys_recvmmsg+0x54e/0xdb0 net/socket.c:2313
 SYSC_recvmmsg+0x29b/0x3e0 net/socket.c:2394
 SyS_recvmmsg+0x76/0xa0 net/socket.c:2378
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc:	Vlad Yasevich <vyasevich@gmail.com>
Cc:	Neil Horman <nhorman@tuxdriver.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/ipv6.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -727,8 +727,10 @@ static int sctp_v6_addr_to_user(struct s
 			sctp_v6_map_v4(addr);
 	}
 
-	if (addr->sa.sa_family == AF_INET)
+	if (addr->sa.sa_family == AF_INET) {
+		memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
 		return sizeof(struct sockaddr_in);
+	}
 	return sizeof(struct sockaddr_in6);
 }
 


Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.9/tcp-better-validation-of-received-ack-sequences.patch
queue-4.9/sctp-sctp_sockaddr_af-must-check-minimal-addr-length-for-af_inet6.patch
queue-4.9/net-fix-possible-out-of-bound-read-in-skb_network_protocol.patch
queue-4.9/pptp-remove-a-buggy-dst-release-in-pptp_connect.patch
queue-4.9/x86-asm-don-t-use-rbp-as-a-temporary-register-in-csum_partial_copy_generic.patch
queue-4.9/net-fool-proof-dev_valid_name.patch
queue-4.9/ipv6-the-entire-ipv6-header-chain-must-fit-the-first-fragment.patch
queue-4.9/vti6-better-validate-user-provided-tunnel-names.patch
queue-4.9/ipv6-sit-better-validate-user-provided-tunnel-names.patch
queue-4.9/ip6_tunnel-better-validate-user-provided-tunnel-names.patch
queue-4.9/sctp-do-not-leak-kernel-memory-to-user-space.patch
queue-4.9/ip_tunnel-better-validate-user-provided-tunnel-names.patch
queue-4.9/skbuff-only-inherit-relevant-tx_flags.patch
queue-4.9/netlink-make-sure-nladdr-has-correct-size-in-netlink_connect.patch
queue-4.9/ip6_gre-better-validate-user-provided-tunnel-names.patch