Re: [PATCH net v2] sctp: verify size of a new chunk in _sctp_make_chunk()

[David Miller]

From: Alexey Kodanev 
Date: Fri,  9 Feb 2018 17:35:23 +0300

> 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:
 ...
> 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 

Applied and queued up for -stable, thanks.

Re: [PATCH net v2] sctp: verify size of a new chunk in _sctp_make_chunk()

[Neil Horman]

On Fri, Feb 09, 2018 at 05:35:23PM +0300, Alexey Kodanev wrote:
> 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:ffae06e4 len:120168
>put:120156 head:7aa47635 data:d991c2de
>tail:0x1d640 end:0xfec0 dev:
> ...
> [  597.976970] [ cut here ]
> [  598.033408] kernel BUG at net/core/skbuff.c:104!
> [  600.314841] Call Trace:
> [  600.345829]  
> [  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]
> [  600.84]  ? 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 
> ---
> 
> v2: account for padding before checking chunklen
> 
>  net/sctp/sm_make_chunk.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 793b05e..d01475f 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1380,9 +1380,14 @@ static struct sctp_chunk *_sctp_make_chunk(const 
> struct sctp_association *asoc,
>   struct sctp_chunk *retval;
>   struct sk_buff *skb;
>   struct sock *sk;
> + int chunklen;
> +
> + chunklen = SCTP_PAD4(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(SCTP_PAD4(sizeof(*chunk_hdr) + paylen), gfp);
> + skb = alloc_skb(chunklen, gfp);
>   if (!skb)
>   goto nodata;
>  
> -- 
> 1.8.3.1
> 
> 
> 
Acked-by: Neil Horman 

Re: [PATCH net v2] sctp: verify size of a new chunk in _sctp_make_chunk()

[Marcelo Ricardo Leitner]

On Fri, Feb 09, 2018 at 05:35:23PM +0300, Alexey Kodanev wrote:
> 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:ffae06e4 len:120168
>put:120156 head:7aa47635 data:d991c2de
>tail:0x1d640 end:0xfec0 dev:
> ...
> [  597.976970] [ cut here ]
> [  598.033408] kernel BUG at net/core/skbuff.c:104!
> [  600.314841] Call Trace:
> [  600.345829]  
> [  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]
> [  600.84]  ? 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 

Acked-by: Marcelo Ricardo Leitner 

Thanks Alexey.

> ---
> 
> v2: account for padding before checking chunklen
> 
>  net/sctp/sm_make_chunk.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 793b05e..d01475f 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -1380,9 +1380,14 @@ static struct sctp_chunk *_sctp_make_chunk(const 
> struct sctp_association *asoc,
>   struct sctp_chunk *retval;
>   struct sk_buff *skb;
>   struct sock *sk;
> + int chunklen;
> +
> + chunklen = SCTP_PAD4(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(SCTP_PAD4(sizeof(*chunk_hdr) + paylen), gfp);
> + skb = alloc_skb(chunklen, gfp);
>   if (!skb)
>   goto nodata;
>  
> -- 
> 1.8.3.1
> 

[PATCH net v2] sctp: verify size of a new chunk in _sctp_make_chunk()

[Alexey Kodanev]

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:ffae06e4 len:120168
   put:120156 head:7aa47635 data:d991c2de
   tail:0x1d640 end:0xfec0 dev:
...
[  597.976970] [ cut here ]
[  598.033408] kernel BUG at net/core/skbuff.c:104!
[  600.314841] Call Trace:
[  600.345829]  
[  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]
[  600.84]  ? 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 
---

v2: account for padding before checking chunklen

 net/sctp/sm_make_chunk.c | 7 ++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 793b05e..d01475f 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1380,9 +1380,14 @@ static struct sctp_chunk *_sctp_make_chunk(const struct 
sctp_association *asoc,
struct sctp_chunk *retval;
struct sk_buff *skb;
struct sock *sk;
+   int chunklen;
+
+   chunklen = SCTP_PAD4(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(SCTP_PAD4(sizeof(*chunk_hdr) + paylen), gfp);
+   skb = alloc_skb(chunklen, gfp);
if (!skb)
goto nodata;
 
-- 
1.8.3.1