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    Subject[PATCH 3.16 14/55] net: ipv6: fib: dont sleep inside atomic lock
    Date
    3.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Benjamin Block <bebl@mageta.org>

    [ Upstream commit 793c3b4000a1ef611ae7e5c89bd2a9c6b776cb5e ]

    The function fib6_commit_metrics() allocates a piece of memory in mode
    GFP_KERNEL while holding an atomic lock from higher up in the stack, in
    the function __ip6_ins_rt(). This produces the following BUG:

    > BUG: sleeping function called from invalid context at mm/slub.c:1250
    > in_atomic(): 1, irqs_disabled(): 0, pid: 2909, name: dhcpcd
    > 2 locks held by dhcpcd/2909:
    > #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff81978e67>] rtnl_lock+0x17/0x20
    > #1: (&tb->tb6_lock){++--+.}, at: [<ffffffff81a6951a>] ip6_route_add+0x65a/0x800
    > CPU: 1 PID: 2909 Comm: dhcpcd Not tainted 3.17.0-rc1 #1
    > Hardware name: ASUS All Series/Q87T, BIOS 0216 10/16/2013
    > 0000000000000008 ffff8800c8f13858 ffffffff81af135a 0000000000000000
    > ffff880212202430 ffff8800c8f13878 ffffffff810f8d3a ffff880212202c98
    > 0000000000000010 ffff8800c8f138c8 ffffffff8121ad0e 0000000000000001
    > Call Trace:
    > [<ffffffff81af135a>] dump_stack+0x4e/0x68
    > [<ffffffff810f8d3a>] __might_sleep+0x10a/0x120
    > [<ffffffff8121ad0e>] kmem_cache_alloc_trace+0x4e/0x190
    > [<ffffffff81a6bcd6>] ? fib6_commit_metrics+0x66/0x110
    > [<ffffffff81a6bcd6>] fib6_commit_metrics+0x66/0x110
    > [<ffffffff81a6cbf3>] fib6_add+0x883/0xa80
    > [<ffffffff81a6951a>] ? ip6_route_add+0x65a/0x800
    > [<ffffffff81a69535>] ip6_route_add+0x675/0x800
    > [<ffffffff81a68f2a>] ? ip6_route_add+0x6a/0x800
    > [<ffffffff81a6990c>] inet6_rtm_newroute+0x5c/0x80
    > [<ffffffff8197cf01>] rtnetlink_rcv_msg+0x211/0x260
    > [<ffffffff81978e67>] ? rtnl_lock+0x17/0x20
    > [<ffffffff81119708>] ? lock_release_holdtime+0x28/0x180
    > [<ffffffff81978e67>] ? rtnl_lock+0x17/0x20
    > [<ffffffff8197ccf0>] ? __rtnl_unlock+0x20/0x20
    > [<ffffffff819a989e>] netlink_rcv_skb+0x6e/0xd0
    > [<ffffffff81978ee5>] rtnetlink_rcv+0x25/0x40
    > [<ffffffff819a8e59>] netlink_unicast+0xd9/0x180
    > [<ffffffff819a9600>] netlink_sendmsg+0x700/0x770
    > [<ffffffff81103735>] ? local_clock+0x25/0x30
    > [<ffffffff8194e83c>] sock_sendmsg+0x6c/0x90
    > [<ffffffff811f98e3>] ? might_fault+0xa3/0xb0
    > [<ffffffff8195ca6d>] ? verify_iovec+0x7d/0xf0
    > [<ffffffff8194ec3e>] ___sys_sendmsg+0x37e/0x3b0
    > [<ffffffff8111ef15>] ? trace_hardirqs_on_caller+0x185/0x220
    > [<ffffffff81af979e>] ? mutex_unlock+0xe/0x10
    > [<ffffffff819a55ec>] ? netlink_insert+0xbc/0xe0
    > [<ffffffff819a65e5>] ? netlink_autobind.isra.30+0x125/0x150
    > [<ffffffff819a6520>] ? netlink_autobind.isra.30+0x60/0x150
    > [<ffffffff819a84f9>] ? netlink_bind+0x159/0x230
    > [<ffffffff811f989a>] ? might_fault+0x5a/0xb0
    > [<ffffffff8194f25e>] ? SYSC_bind+0x7e/0xd0
    > [<ffffffff8194f8cd>] __sys_sendmsg+0x4d/0x80
    > [<ffffffff8194f912>] SyS_sendmsg+0x12/0x20
    > [<ffffffff81afc692>] system_call_fastpath+0x16/0x1b

    Fixing this by replacing the mode GFP_KERNEL with GFP_ATOMIC.

    Signed-off-by: Benjamin Block <bebl@mageta.org>
    Acked-by: David Rientjes <rientjes@google.com>
    Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv6/ip6_fib.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/net/ipv6/ip6_fib.c
    +++ b/net/ipv6/ip6_fib.c
    @@ -643,7 +643,7 @@ static int fib6_commit_metrics(struct ds
    if (dst->flags & DST_HOST) {
    mp = dst_metrics_write_ptr(dst);
    } else {
    - mp = kzalloc(sizeof(u32) * RTAX_MAX, GFP_KERNEL);
    + mp = kzalloc(sizeof(u32) * RTAX_MAX, GFP_ATOMIC);
    if (!mp)
    return -ENOMEM;
    dst_init_metrics(dst, mp, 0);



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