3.2.102-rc1 review patch. If anyone has any objections, please let me know.
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From: Alexey Kodanev alexey.kodanev@oracle.com
commit 07f2c7ab6f8d0a7e7c5764c4e6cc9c52951b9d9c upstream.
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@oracle.com Acked-by: Marcelo Ricardo Leitner marcelo.leinter@gmail.com Acked-by: Neil Horman nhorman@tuxdriver.com Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 3.2: - Keep using WORD_ROUND() instead of SCTP_PAD4() - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/sctp/sm_make_chunk.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -1324,10 +1324,14 @@ struct sctp_chunk *sctp_make_chunk(const sctp_chunkhdr_t *chunk_hdr; struct sk_buff *skb; struct sock *sk; + int chunklen; + + chunklen = WORD_ROUND(sizeof(*chunk_hdr) + paylen); + 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;