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    Subject[PATCH 5.4 033/408] net/sched: act_tunnel_key: fix OOB write in case of IPv6 ERSPAN tunnels
    Date
    From: Davide Caratti <dcaratti@redhat.com>

    [ Upstream commit a7a12b5a0f950bc6b9f7153390634ea798738db9 ]

    the following command

    # tc action add action tunnel_key \
    > set src_ip 2001:db8::1 dst_ip 2001:db8::2 id 10 erspan_opts 1:6789:0:0

    generates the following splat:

    BUG: KASAN: slab-out-of-bounds in tunnel_key_copy_opts+0xcc9/0x1010 [act_tunnel_key]
    Write of size 4 at addr ffff88813f5f1cc8 by task tc/873

    CPU: 2 PID: 873 Comm: tc Not tainted 5.9.0+ #282
    Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
    Call Trace:
    dump_stack+0x99/0xcb
    print_address_description.constprop.7+0x1e/0x230
    kasan_report.cold.13+0x37/0x7c
    tunnel_key_copy_opts+0xcc9/0x1010 [act_tunnel_key]
    tunnel_key_init+0x160c/0x1f40 [act_tunnel_key]
    tcf_action_init_1+0x5b5/0x850
    tcf_action_init+0x15d/0x370
    tcf_action_add+0xd9/0x2f0
    tc_ctl_action+0x29b/0x3a0
    rtnetlink_rcv_msg+0x341/0x8d0
    netlink_rcv_skb+0x120/0x380
    netlink_unicast+0x439/0x630
    netlink_sendmsg+0x719/0xbf0
    sock_sendmsg+0xe2/0x110
    ____sys_sendmsg+0x5ba/0x890
    ___sys_sendmsg+0xe9/0x160
    __sys_sendmsg+0xd3/0x170
    do_syscall_64+0x33/0x40
    entry_SYSCALL_64_after_hwframe+0x44/0xa9
    RIP: 0033:0x7f872a96b338
    Code: 89 02 48 c7 c0 ff ff ff ff eb b5 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 25 43 2c 00 8b 00 85 c0 75 17 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 41 89 d4 55
    RSP: 002b:00007ffffe367518 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
    RAX: ffffffffffffffda RBX: 000000005f8f5aed RCX: 00007f872a96b338
    RDX: 0000000000000000 RSI: 00007ffffe367580 RDI: 0000000000000003
    RBP: 0000000000000000 R08: 0000000000000001 R09: 000000000000001c
    R10: 000000000000000b R11: 0000000000000246 R12: 0000000000000001
    R13: 0000000000686760 R14: 0000000000000601 R15: 0000000000000000

    Allocated by task 873:
    kasan_save_stack+0x19/0x40
    __kasan_kmalloc.constprop.7+0xc1/0xd0
    __kmalloc+0x151/0x310
    metadata_dst_alloc+0x20/0x40
    tunnel_key_init+0xfff/0x1f40 [act_tunnel_key]
    tcf_action_init_1+0x5b5/0x850
    tcf_action_init+0x15d/0x370
    tcf_action_add+0xd9/0x2f0
    tc_ctl_action+0x29b/0x3a0
    rtnetlink_rcv_msg+0x341/0x8d0
    netlink_rcv_skb+0x120/0x380
    netlink_unicast+0x439/0x630
    netlink_sendmsg+0x719/0xbf0
    sock_sendmsg+0xe2/0x110
    ____sys_sendmsg+0x5ba/0x890
    ___sys_sendmsg+0xe9/0x160
    __sys_sendmsg+0xd3/0x170
    do_syscall_64+0x33/0x40
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

    The buggy address belongs to the object at ffff88813f5f1c00
    which belongs to the cache kmalloc-256 of size 256
    The buggy address is located 200 bytes inside of
    256-byte region [ffff88813f5f1c00, ffff88813f5f1d00)
    The buggy address belongs to the page:
    page:0000000011b48a19 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13f5f0
    head:0000000011b48a19 order:1 compound_mapcount:0
    flags: 0x17ffffc0010200(slab|head)
    raw: 0017ffffc0010200 0000000000000000 0000000d00000001 ffff888107c43400
    raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
    ffff88813f5f1b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    ffff88813f5f1c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    >ffff88813f5f1c80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
    ^
    ffff88813f5f1d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    ffff88813f5f1d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

    using IPv6 tunnels, act_tunnel_key allocates a fixed amount of memory for
    the tunnel metadata, but then it expects additional bytes to store tunnel
    specific metadata with tunnel_key_copy_opts().

    Fix the arguments of __ipv6_tun_set_dst(), so that 'md_size' contains the
    size previously computed by tunnel_key_get_opts_len(), like it's done for
    IPv4 tunnels.

    Fixes: 0ed5269f9e41 ("net/sched: add tunnel option support to act_tunnel_key")
    Reported-by: Shuang Li <shuali@redhat.com>
    Signed-off-by: Davide Caratti <dcaratti@redhat.com>
    Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
    Link: https://lore.kernel.org/r/36ebe969f6d13ff59912d6464a4356fe6f103766.1603231100.git.dcaratti@redhat.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sched/act_tunnel_key.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/net/sched/act_tunnel_key.c
    +++ b/net/sched/act_tunnel_key.c
    @@ -315,7 +315,7 @@ static int tunnel_key_init(struct net *n

    metadata = __ipv6_tun_set_dst(&saddr, &daddr, tos, ttl, dst_port,
    0, flags,
    - key_id, 0);
    + key_id, opts_len);
    } else {
    NL_SET_ERR_MSG(extack, "Missing either ipv4 or ipv6 src and dst");
    ret = -EINVAL;

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