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    Subject[PATCH AUTOSEL 4.19 12/52] batman-adv: fix uninit-value in batadv_netlink_get_ifindex()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 3ee1bb7aae97324ec9078da1f00cb2176919563f ]

    batadv_netlink_get_ifindex() needs to make sure user passed
    a correct u32 attribute.

    syzbot reported :
    BUG: KMSAN: uninit-value in batadv_netlink_dump_hardif+0x70d/0x880 net/batman-adv/netlink.c:968
    CPU: 1 PID: 11705 Comm: syz-executor888 Not tainted 5.1.0+ #1
    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+0x191/0x1f0 lib/dump_stack.c:113
    kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
    __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
    batadv_netlink_dump_hardif+0x70d/0x880 net/batman-adv/netlink.c:968
    genl_lock_dumpit+0xc6/0x130 net/netlink/genetlink.c:482
    netlink_dump+0xa84/0x1ab0 net/netlink/af_netlink.c:2253
    __netlink_dump_start+0xa3a/0xb30 net/netlink/af_netlink.c:2361
    genl_family_rcv_msg net/netlink/genetlink.c:550 [inline]
    genl_rcv_msg+0xfc1/0x1a40 net/netlink/genetlink.c:627
    netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2486
    genl_rcv+0x63/0x80 net/netlink/genetlink.c:638
    netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
    netlink_unicast+0xf3e/0x1020 net/netlink/af_netlink.c:1337
    netlink_sendmsg+0x127e/0x12f0 net/netlink/af_netlink.c:1926
    sock_sendmsg_nosec net/socket.c:651 [inline]
    sock_sendmsg net/socket.c:661 [inline]
    ___sys_sendmsg+0xcc6/0x1200 net/socket.c:2260
    __sys_sendmsg net/socket.c:2298 [inline]
    __do_sys_sendmsg net/socket.c:2307 [inline]
    __se_sys_sendmsg+0x305/0x460 net/socket.c:2305
    __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2305
    do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
    entry_SYSCALL_64_after_hwframe+0x63/0xe7
    RIP: 0033:0x440209

    Fixes: b60620cf567b ("batman-adv: netlink: hardif query")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Signed-off-by: Sven Eckelmann <sven@narfation.org>
    Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/batman-adv/netlink.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
    index 0d9459b69bdb8..c32820963b8e7 100644
    --- a/net/batman-adv/netlink.c
    +++ b/net/batman-adv/netlink.c
    @@ -118,7 +118,7 @@ batadv_netlink_get_ifindex(const struct nlmsghdr *nlh, int attrtype)
    {
    struct nlattr *attr = nlmsg_find_attr(nlh, GENL_HDRLEN, attrtype);

    - return attr ? nla_get_u32(attr) : 0;
    + return (attr && nla_len(attr) == sizeof(u32)) ? nla_get_u32(attr) : 0;
    }

    /**
    --
    2.20.1
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