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    Subject[PATCH 4.16 03/68] slip: Check if rstate is initialized before uncompressing
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Tejaswi Tanikella <tejaswit@codeaurora.org>


    [ Upstream commit 3f01ddb962dc506916c243f9524e8bef97119b77 ]

    On receiving a packet the state index points to the rstate which must be
    used to fill up IP and TCP headers. But if the state index points to a
    rstate which is unitialized, i.e. filled with zeros, it gets stuck in an
    infinite loop inside ip_fast_csum trying to compute the ip checsum of a
    header with zero length.

    89.666953: <2> [<ffffff9dd3e94d38>] slhc_uncompress+0x464/0x468
    89.666965: <2> [<ffffff9dd3e87d88>] ppp_receive_nonmp_frame+0x3b4/0x65c
    89.666978: <2> [<ffffff9dd3e89dd4>] ppp_receive_frame+0x64/0x7e0
    89.666991: <2> [<ffffff9dd3e8a708>] ppp_input+0x104/0x198
    89.667005: <2> [<ffffff9dd3e93868>] pppopns_recv_core+0x238/0x370
    89.667027: <2> [<ffffff9dd4428fc8>] __sk_receive_skb+0xdc/0x250
    89.667040: <2> [<ffffff9dd3e939e4>] pppopns_recv+0x44/0x60
    89.667053: <2> [<ffffff9dd4426848>] __sock_queue_rcv_skb+0x16c/0x24c
    89.667065: <2> [<ffffff9dd4426954>] sock_queue_rcv_skb+0x2c/0x38
    89.667085: <2> [<ffffff9dd44f7358>] raw_rcv+0x124/0x154
    89.667098: <2> [<ffffff9dd44f7568>] raw_local_deliver+0x1e0/0x22c
    89.667117: <2> [<ffffff9dd44c8ba0>] ip_local_deliver_finish+0x70/0x24c
    89.667131: <2> [<ffffff9dd44c92f4>] ip_local_deliver+0x100/0x10c

    ./scripts/faddr2line vmlinux slhc_uncompress+0x464/0x468 output:
    ip_fast_csum at arch/arm64/include/asm/checksum.h:40
    (inlined by) slhc_uncompress at drivers/net/slip/slhc.c:615

    Adding a variable to indicate if the current rstate is initialized. If
    such a packet arrives, move to toss state.

    Signed-off-by: Tejaswi Tanikella <tejaswit@codeaurora.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/slip/slhc.c | 5 +++++
    include/net/slhc_vj.h | 1 +
    2 files changed, 6 insertions(+)

    --- a/drivers/net/slip/slhc.c
    +++ b/drivers/net/slip/slhc.c
    @@ -509,6 +509,10 @@ slhc_uncompress(struct slcompress *comp,
    if(x < 0 || x > comp->rslot_limit)
    goto bad;

    + /* Check if the cstate is initialized */
    + if (!comp->rstate[x].initialized)
    + goto bad;
    +
    comp->flags &=~ SLF_TOSS;
    comp->recv_current = x;
    } else {
    @@ -673,6 +677,7 @@ slhc_remember(struct slcompress *comp, u
    if (cs->cs_tcp.doff > 5)
    memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
    cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
    + cs->initialized = true;
    /* Put headers back on packet
    * Neither header checksum is recalculated
    */
    --- a/include/net/slhc_vj.h
    +++ b/include/net/slhc_vj.h
    @@ -127,6 +127,7 @@ typedef __u32 int32;
    */
    struct cstate {
    byte_t cs_this; /* connection id number (xmit) */
    + bool initialized; /* true if initialized */
    struct cstate *next; /* next in ring (xmit) */
    struct iphdr cs_ip; /* ip/tcp hdr from most recent packet */
    struct tcphdr cs_tcp;

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