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

Subsystems: networking [general], sctp protocol, the rest

STALE3148d

4 messages, 4 authors, 2018-02-09 · open the first message on its own page

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

From: Alexey Kodanev <hidden>
Date: 2018-02-09 14:31:48

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 <redacted>
---

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

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

From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2018-02-09 14:41:04

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: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 <redacted>

Acked-by: Marcelo Ricardo Leitner <redacted>

Thanks Alexey.

quoted hunk

---

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

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

From: Neil Horman <nhorman@tuxdriver.com>
Date: 2018-02-09 15:03:00

On Fri, Feb 09, 2018 at 05:35:23PM +0300, Alexey Kodanev wrote:

quoted hunk

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 <redacted>
---

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 <nhorman@tuxdriver.com>

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

From: David Miller <davem@davemloft.net>
Date: 2018-02-09 19:32:24

From: Alexey Kodanev <redacted>
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 <redacted>

Applied and queued up for -stable, thanks.

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