From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejaswi Tanikella Date: Thu, 29 Mar 2018 09:58:15 +0000 Subject: [PATCH] slip: Check if rstate is initialized before uncompressing Message-Id: <20180329095758.GA510@tejaswit-linux.qualcomm.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ppp@vger.kernel.org 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, watch-dog bites. It gets stuck in an infinite loop inside ip_fast_csum trying to compute the ip checsum of a header with length zero. 89.666953: <2> [] slhc_uncompress+0x464/0x468 89.666965: <2> [] ppp_receive_nonmp_frame+0x3b4/0x65c 89.666978: <2> [] ppp_receive_frame+0x64/0x7e0 89.666991: <2> [] ppp_input+0x104/0x198 89.667005: <2> [] pppopns_recv_core+0x238/0x370 89.667027: <2> [] __sk_receive_skb+0xdc/0x250 89.667040: <2> [] pppopns_recv+0x44/0x60 89.667053: <2> [] __sock_queue_rcv_skb+0x16c/0x24c 89.667065: <2> [] sock_queue_rcv_skb+0x2c/0x38 89.667085: <2> [] raw_rcv+0x124/0x154 89.667098: <2> [] raw_local_deliver+0x1e0/0x22c 89.667117: <2> [] ip_local_deliver_finish+0x70/0x24c 89.667131: <2> [] 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 --- drivers/net/slip/slhc.c | 5 +++++ include/net/slhc_vj.h | 1 + 2 files changed, 6 insertions(+) diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c index 5782733..e710b0b 100644 --- a/drivers/net/slip/slhc.c +++ b/drivers/net/slip/slhc.c @@ -509,6 +509,10 @@ struct slcompress * 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 @@ struct slcompress * 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 = 1; /* Put headers back on packet * Neither header checksum is recalculated */ diff --git a/include/net/slhc_vj.h b/include/net/slhc_vj.h index 8716d59..d673365 100644 --- a/include/net/slhc_vj.h +++ b/include/net/slhc_vj.h @@ -127,6 +127,7 @@ */ struct cstate { byte_t cs_this; /* connection id number (xmit) */ + byte_t initialized; /* non-zero if initialized */ struct cstate *next; /* next in ring (xmit) */ struct iphdr cs_ip; /* ip/tcp hdr from most recent packet */ struct tcphdr cs_tcp; -- 1.9.1