On Fri, 2018-03-09 at 16:18 -0800, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx> > > > [ Upstream commit 07f2c7ab6f8d0a7e7c5764c4e6cc9c52951b9d9c ] > > When SCTP makes INIT or INIT_ACK packet the total chunk length > can exceed SCTP_MAX_CHUNK_LEN which leads to kernel panic when > transmitting these packets, e.g. the crash on sending INIT_ACK: > > [ 597.804948] skbuff: skb_over_panic: text:00000000ffae06e4 len:120168 > put:120156 head:000000007aa47635 data:00000000d991c2de > tail:0x1d640 end:0xfec0 dev:<NULL> > ... > [ 597.976970] ------------[ cut here ]------------ > [ 598.033408] kernel BUG at net/core/skbuff.c:104! > [ 600.314841] Call Trace: > [ 600.345829] <IRQ> > [ 600.371639] ? sctp_packet_transmit+0x2095/0x26d0 [sctp] > [ 600.436934] skb_put+0x16c/0x200 > [ 600.477295] sctp_packet_transmit+0x2095/0x26d0 [sctp] > [ 600.540630] ? sctp_packet_config+0x890/0x890 [sctp] > [ 600.601781] ? __sctp_packet_append_chunk+0x3b4/0xd00 [sctp] > [ 600.671356] ? sctp_cmp_addr_exact+0x3f/0x90 [sctp] > [ 600.731482] sctp_outq_flush+0x663/0x30d0 [sctp] > [ 600.788565] ? sctp_make_init+0xbf0/0xbf0 [sctp] > [ 600.845555] ? sctp_check_transmitted+0x18f0/0x18f0 [sctp] > [ 600.912945] ? sctp_outq_tail+0x631/0x9d0 [sctp] > [ 600.969936] sctp_cmd_interpreter.isra.22+0x3be1/0x5cb0 [sctp] > [ 601.041593] ? sctp_sf_do_5_1B_init+0x85f/0xc30 [sctp] > [ 601.104837] ? sctp_generate_t1_cookie_event+0x20/0x20 [sctp] > [ 601.175436] ? sctp_eat_data+0x1710/0x1710 [sctp] > [ 601.233575] sctp_do_sm+0x182/0x560 [sctp] > [ 601.284328] ? sctp_has_association+0x70/0x70 [sctp] > [ 601.345586] ? sctp_rcv+0xef4/0x32f0 [sctp] > [ 601.397478] ? sctp6_rcv+0xa/0x20 [sctp] > ... > > Here the chunk size for INIT_ACK packet becomes too big, mostly > because of the state cookie (INIT packet has large size with > many address parameters), plus additional server parameters. > > Later this chunk causes the panic in skb_put_data(): > > skb_packet_transmit() > sctp_packet_pack() > skb_put_data(nskb, chunk->skb->data, chunk->skb->len); > > 'nskb' (head skb) was previously allocated with packet->size > from u16 'chunk->chunk_hdr->length'. > > As suggested by Marcelo we should check the chunk's length in > _sctp_make_chunk() before trying to allocate skb for it and > discard a chunk if its size bigger than SCTP_MAX_CHUNK_LEN. > > > Signed-off-by: Alexey Kodanev <alexey.kodanev@xxxxxxxxxx> > > Acked-by: Marcelo Ricardo Leitner <marcelo.leinter@xxxxxxxxx> > > Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- > net/sctp/sm_make_chunk.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > --- a/net/sctp/sm_make_chunk.c > +++ b/net/sctp/sm_make_chunk.c > @@ -1367,10 +1367,14 @@ static struct sctp_chunk *_sctp_make_chu > sctp_chunkhdr_t *chunk_hdr; > struct sk_buff *skb; > struct sock *sk; > + int chunklen; > + > + chunklen = sizeof(*chunk_hdr) + paylen; I think this length still needs to be rounded up (with WORD_ROUND here, instead of SCTP_PAD4 upstream). Ben. > + if (chunklen > SCTP_MAX_CHUNK_LEN) > + goto nodata; > > /* No need to allocate LL here, as this is only a chunk. */ > - skb = alloc_skb(WORD_ROUND(sizeof(sctp_chunkhdr_t) + paylen), > - GFP_ATOMIC); > + skb = alloc_skb(chunklen, GFP_ATOMIC); > if (!skb) > goto nodata; > > > > -- Ben Hutchings Software Developer, Codethink Ltd.