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    Subject[PATCH 4.20 122/183] batman-adv: fix uninit-value in batadv_interface_tx()
    Date
    4.20-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 4ffcbfac60642f63ae3d80891f573ba7e94a265c ]

    KMSAN reported batadv_interface_tx() was possibly using a
    garbage value [1]

    batadv_get_vid() does have a pskb_may_pull() call
    but batadv_interface_tx() does not actually make sure
    this did not fail.

    [1]
    BUG: KMSAN: uninit-value in batadv_interface_tx+0x908/0x1e40 net/batman-adv/soft-interface.c:231
    CPU: 0 PID: 10006 Comm: syz-executor469 Not tainted 4.20.0-rc7+ #5
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x173/0x1d0 lib/dump_stack.c:113
    kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:613
    __msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313
    batadv_interface_tx+0x908/0x1e40 net/batman-adv/soft-interface.c:231
    __netdev_start_xmit include/linux/netdevice.h:4356 [inline]
    netdev_start_xmit include/linux/netdevice.h:4365 [inline]
    xmit_one net/core/dev.c:3257 [inline]
    dev_hard_start_xmit+0x607/0xc40 net/core/dev.c:3273
    __dev_queue_xmit+0x2e42/0x3bc0 net/core/dev.c:3843
    dev_queue_xmit+0x4b/0x60 net/core/dev.c:3876
    packet_snd net/packet/af_packet.c:2928 [inline]
    packet_sendmsg+0x8306/0x8f30 net/packet/af_packet.c:2953
    sock_sendmsg_nosec net/socket.c:621 [inline]
    sock_sendmsg net/socket.c:631 [inline]
    __sys_sendto+0x8c4/0xac0 net/socket.c:1788
    __do_sys_sendto net/socket.c:1800 [inline]
    __se_sys_sendto+0x107/0x130 net/socket.c:1796
    __x64_sys_sendto+0x6e/0x90 net/socket.c:1796
    do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
    entry_SYSCALL_64_after_hwframe+0x63/0xe7
    RIP: 0033:0x441889
    Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 bb 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
    RSP: 002b:00007ffdda6fd468 EFLAGS: 00000216 ORIG_RAX: 000000000000002c
    RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000441889
    RDX: 000000000000000e RSI: 00000000200000c0 RDI: 0000000000000003
    RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000216 R12: 00007ffdda6fd4c0
    R13: 00007ffdda6fd4b0 R14: 0000000000000000 R15: 0000000000000000

    Uninit was created at:
    kmsan_save_stack_with_flags mm/kmsan/kmsan.c:204 [inline]
    kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:158
    kmsan_kmalloc+0xa6/0x130 mm/kmsan/kmsan_hooks.c:176
    kmsan_slab_alloc+0xe/0x10 mm/kmsan/kmsan_hooks.c:185
    slab_post_alloc_hook mm/slab.h:446 [inline]
    slab_alloc_node mm/slub.c:2759 [inline]
    __kmalloc_node_track_caller+0xe18/0x1030 mm/slub.c:4383
    __kmalloc_reserve net/core/skbuff.c:137 [inline]
    __alloc_skb+0x309/0xa20 net/core/skbuff.c:205
    alloc_skb include/linux/skbuff.h:998 [inline]
    alloc_skb_with_frags+0x1c7/0xac0 net/core/skbuff.c:5220
    sock_alloc_send_pskb+0xafd/0x10e0 net/core/sock.c:2083
    packet_alloc_skb net/packet/af_packet.c:2781 [inline]
    packet_snd net/packet/af_packet.c:2872 [inline]
    packet_sendmsg+0x661a/0x8f30 net/packet/af_packet.c:2953
    sock_sendmsg_nosec net/socket.c:621 [inline]
    sock_sendmsg net/socket.c:631 [inline]
    __sys_sendto+0x8c4/0xac0 net/socket.c:1788
    __do_sys_sendto net/socket.c:1800 [inline]
    __se_sys_sendto+0x107/0x130 net/socket.c:1796
    __x64_sys_sendto+0x6e/0x90 net/socket.c:1796
    do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
    entry_SYSCALL_64_after_hwframe+0x63/0xe7

    Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Cc: Marek Lindner <mareklindner@neomailbox.ch>
    Cc: Simon Wunderlich <sw@simonwunderlich.de>
    Cc: Antonio Quartulli <a@unstable.cc>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/batman-adv/soft-interface.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/net/batman-adv/soft-interface.c
    +++ b/net/batman-adv/soft-interface.c
    @@ -227,6 +227,8 @@ static netdev_tx_t batadv_interface_tx(s

    switch (ntohs(ethhdr->h_proto)) {
    case ETH_P_8021Q:
    + if (!pskb_may_pull(skb, sizeof(*vhdr)))
    + goto dropped;
    vhdr = vlan_eth_hdr(skb);

    /* drop batman-in-batman packets to prevent loops */

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