Re: [PATCH 1/1] net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero

6 messages, 5 authors, 2023-05-19 · open the first message on its own page

Re: [PATCH 1/1] net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero

From: Bjørn Mork <bjorn@mork.no>
Date: 2021-12-03 14:53:06

Lee Jones [off-list ref] writes:

quoted hunk

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 24753a4da7e60..e303b522efb50 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c

@@ -181,6 +181,8 @@ static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx)
 		min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32);
 
 	max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
+	if (max == 0)
+		max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set */
 
 	/* some devices set dwNtbOutMaxSize too low for the above default */
 	min = min(min, max);

I believe this is the best possible fix, considering the regressions
anything stricter might cause.

We know of at least one MBIM device where dwNtbOutMaxSize is as low as
2048.

According to the MBIM spec, the minimum and default value for
wMaxSegmentSize is also 2048.  This implies that the calculated "min"
value is at least 2076, which is why we need that odd looking

  min = min(min, max);

So let's just fix this specific zero case without breaking the
non-conforming devices.


Reviewed-by: Bjørn Mork <bjorn@mork.no>

Re: [PATCH 1/1] net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero

From: Jakub Kicinski <kuba@kernel.org>
Date: 2021-12-04 00:57:53

On Fri, 03 Dec 2021 15:52:48 +0100 Bjørn Mork wrote:

Lee Jones [off-list ref] writes:

quoted

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 24753a4da7e60..e303b522efb50 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c

@@ -181,6 +181,8 @@ static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx)
 		min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32);
 
 	max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
+	if (max == 0)
+		max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set */
 
 	/* some devices set dwNtbOutMaxSize too low for the above default */
 	min = min(min, max);

I believe this is the best possible fix, considering the regressions
anything stricter might cause.

We know of at least one MBIM device where dwNtbOutMaxSize is as low as
2048.

According to the MBIM spec, the minimum and default value for
wMaxSegmentSize is also 2048.  This implies that the calculated "min"
value is at least 2076, which is why we need that odd looking

  min = min(min, max);

So let's just fix this specific zero case without breaking the
non-conforming devices.


Reviewed-by: Bjørn Mork <bjorn@mork.no>

Applied to net, thanks!

[PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize

From: Tudor Ambarus <tudor.ambarus@linaro.org>
Date: 2023-05-17 13:38:25

Currently in cdc_ncm_check_tx_max(), if dwNtbOutMaxSize is lower than
the calculated "min" value, but greater than zero, the logic sets
tx_max to dwNtbOutMaxSize. This is then used to allocate a new SKB in
cdc_ncm_fill_tx_frame() where all the data is handled.

For small values of dwNtbOutMaxSize the memory allocated during
alloc_skb(dwNtbOutMaxSize, GFP_ATOMIC) will have the same size, due to
how size is aligned at alloc time:
	size = SKB_DATA_ALIGN(size);
        size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
Thus we hit the same bug that we tried to squash with
commit 2be6d4d16a084 ("net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero")

Low values of dwNtbOutMaxSize do not cause an issue presently because at
alloc_skb() time more memory (512b) is allocated than required for the
SKB headers alone (320b), leaving some space (512b - 320b = 192b)
for CDC data (172b).

However, if more elements (for example 3 x u64 = [24b]) were added to
one of the SKB header structs, say 'struct skb_shared_info',
increasing its original size (320b [320b aligned]) to something larger
(344b [384b aligned]), then suddenly the CDC data (172b) no longer
fits in the spare SKB data area (512b - 384b = 128b).

Consequently the SKB bounds checking semantics fails and panics:

skbuff: skb_over_panic: text:ffffffff831f755b len:184 put:172 head:ffff88811f1c6c00 data:ffff88811f1c6c00 tail:0xb8 end:0x80 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:113!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 57 Comm: kworker/0:2 Not tainted 5.15.106-syzkaller-00249-g19c0ed55a470 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Workqueue: mld mld_ifc_work
RIP: 0010:skb_panic net/core/skbuff.c:113 [inline]
RIP: 0010:skb_over_panic+0x14c/0x150 net/core/skbuff.c:118
[snip]
Call Trace:
 <TASK>
 skb_put+0x151/0x210 net/core/skbuff.c:2047
 skb_put_zero include/linux/skbuff.h:2422 [inline]
 cdc_ncm_ndp16 drivers/net/usb/cdc_ncm.c:1131 [inline]
 cdc_ncm_fill_tx_frame+0x11ab/0x3da0 drivers/net/usb/cdc_ncm.c:1308
 cdc_ncm_tx_fixup+0xa3/0x100

Deal with too low values of dwNtbOutMaxSize, clamp it in the range
[USB_CDC_NCM_NTB_MIN_OUT_SIZE, CDC_NCM_NTB_MAX_SIZE_TX]. We ensure
enough data space is allocated to handle CDC data by making sure
dwNtbOutMaxSize is not smaller than USB_CDC_NCM_NTB_MIN_OUT_SIZE.

Fixes: 289507d3364f ("net: cdc_ncm: use sysfs for rx/tx aggregation tuning")
Cc: stable@vger.kernel.org
Reported-by: syzbot+9f575a1f15fc0c01ed69@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=b982f1059506db48409d
Link: https://lore.kernel.org/all/20211202143437.1411410-1-lee.jones@linaro.org/
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
 drivers/net/usb/cdc_ncm.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 6ce8f4f0c70e..db05622f1f70 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c

@@ -181,9 +181,12 @@ static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx)
 	else
 		min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32);
 
-	max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
-	if (max == 0)
+	if (le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize) == 0)
 		max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set */
+	else
+		max = clamp_t(u32, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize),
+			      USB_CDC_NCM_NTB_MIN_OUT_SIZE,
+			      CDC_NCM_NTB_MAX_SIZE_TX);
 
 	/* some devices set dwNtbOutMaxSize too low for the above default */
 	min = min(min, max);

@@ -1244,6 +1247,9 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 			 * further.
 			 */
 			if (skb_out == NULL) {
+				/* If even the smallest allocation fails, abort. */
+				if (ctx->tx_curr_size == USB_CDC_NCM_NTB_MIN_OUT_SIZE)
+					goto alloc_failed;
 				ctx->tx_low_mem_max_cnt = min(ctx->tx_low_mem_max_cnt + 1,
 							      (unsigned)CDC_NCM_LOW_MEM_MAX_CNT);
 				ctx->tx_low_mem_val = ctx->tx_low_mem_max_cnt;

@@ -1262,13 +1268,8 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 			skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);
 
 			/* No allocation possible so we will abort */
-			if (skb_out == NULL) {
-				if (skb != NULL) {
-					dev_kfree_skb_any(skb);
-					dev->net->stats.tx_dropped++;
-				}
-				goto exit_no_skb;
-			}
+			if (!skb_out)
+				goto alloc_failed;
 			ctx->tx_low_mem_val--;
 		}
 		if (ctx->is_ndp16) {

@@ -1461,6 +1462,11 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 
 	return skb_out;
 
+alloc_failed:
+	if (skb) {
+		dev_kfree_skb_any(skb);
+		dev->net->stats.tx_dropped++;
+	}
 exit_no_skb:
 	/* Start timer, if there is a remaining non-empty skb */
 	if (ctx->tx_curr_skb != NULL && n > 0)

-- 
2.40.1.606.ga4b1b128d6-goog

[PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize

From: Tudor Ambarus <tudor.ambarus@linaro.org>
Date: 2023-05-17 13:38:30

Currently in cdc_ncm_check_tx_max(), if dwNtbOutMaxSize is lower than
the calculated "min" value, but greater than zero, the logic sets
tx_max to dwNtbOutMaxSize. This is then used to allocate a new SKB in
cdc_ncm_fill_tx_frame() where all the data is handled.

For small values of dwNtbOutMaxSize the memory allocated during
alloc_skb(dwNtbOutMaxSize, GFP_ATOMIC) will have the same size, due to
how size is aligned at alloc time:
	size = SKB_DATA_ALIGN(size);
        size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
Thus we hit the same bug that we tried to squash with
commit 2be6d4d16a084 ("net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero")

Low values of dwNtbOutMaxSize do not cause an issue presently because at
alloc_skb() time more memory (512b) is allocated than required for the
SKB headers alone (320b), leaving some space (512b - 320b = 192b)
for CDC data (172b).

However, if more elements (for example 3 x u64 = [24b]) were added to
one of the SKB header structs, say 'struct skb_shared_info',
increasing its original size (320b [320b aligned]) to something larger
(344b [384b aligned]), then suddenly the CDC data (172b) no longer
fits in the spare SKB data area (512b - 384b = 128b).

Consequently the SKB bounds checking semantics fails and panics:

skbuff: skb_over_panic: text:ffffffff831f755b len:184 put:172 head:ffff88811f1c6c00 data:ffff88811f1c6c00 tail:0xb8 end:0x80 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:113!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 57 Comm: kworker/0:2 Not tainted 5.15.106-syzkaller-00249-g19c0ed55a470 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Workqueue: mld mld_ifc_work
RIP: 0010:skb_panic net/core/skbuff.c:113 [inline]
RIP: 0010:skb_over_panic+0x14c/0x150 net/core/skbuff.c:118
[snip]
Call Trace:
 <TASK>
 skb_put+0x151/0x210 net/core/skbuff.c:2047
 skb_put_zero include/linux/skbuff.h:2422 [inline]
 cdc_ncm_ndp16 drivers/net/usb/cdc_ncm.c:1131 [inline]
 cdc_ncm_fill_tx_frame+0x11ab/0x3da0 drivers/net/usb/cdc_ncm.c:1308
 cdc_ncm_tx_fixup+0xa3/0x100

Deal with too low values of dwNtbOutMaxSize, clamp it in the range
[USB_CDC_NCM_NTB_MIN_OUT_SIZE, CDC_NCM_NTB_MAX_SIZE_TX]. We ensure
enough data space is allocated to handle CDC data by making sure
dwNtbOutMaxSize is not smaller than USB_CDC_NCM_NTB_MIN_OUT_SIZE.

Fixes: 289507d3364f ("net: cdc_ncm: use sysfs for rx/tx aggregation tuning")
Cc: stable@vger.kernel.org
Reported-by: syzbot+9f575a1f15fc0c01ed69@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=b982f1059506db48409d
Link: https://lore.kernel.org/all/20211202143437.1411410-1-lee.jones@linaro.org/
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
 drivers/net/usb/cdc_ncm.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 6ce8f4f0c70e..db05622f1f70 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c

@@ -181,9 +181,12 @@ static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx)
 	else
 		min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32);
 
-	max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
-	if (max == 0)
+	if (le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize) == 0)
 		max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set */
+	else
+		max = clamp_t(u32, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize),
+			      USB_CDC_NCM_NTB_MIN_OUT_SIZE,
+			      CDC_NCM_NTB_MAX_SIZE_TX);
 
 	/* some devices set dwNtbOutMaxSize too low for the above default */
 	min = min(min, max);

@@ -1244,6 +1247,9 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 			 * further.
 			 */
 			if (skb_out == NULL) {
+				/* If even the smallest allocation fails, abort. */
+				if (ctx->tx_curr_size == USB_CDC_NCM_NTB_MIN_OUT_SIZE)
+					goto alloc_failed;
 				ctx->tx_low_mem_max_cnt = min(ctx->tx_low_mem_max_cnt + 1,
 							      (unsigned)CDC_NCM_LOW_MEM_MAX_CNT);
 				ctx->tx_low_mem_val = ctx->tx_low_mem_max_cnt;

@@ -1262,13 +1268,8 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 			skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);
 
 			/* No allocation possible so we will abort */
-			if (skb_out == NULL) {
-				if (skb != NULL) {
-					dev_kfree_skb_any(skb);
-					dev->net->stats.tx_dropped++;
-				}
-				goto exit_no_skb;
-			}
+			if (!skb_out)
+				goto alloc_failed;
 			ctx->tx_low_mem_val--;
 		}
 		if (ctx->is_ndp16) {

@@ -1461,6 +1462,11 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 
 	return skb_out;
 
+alloc_failed:
+	if (skb) {
+		dev_kfree_skb_any(skb);
+		dev->net->stats.tx_dropped++;
+	}
 exit_no_skb:
 	/* Start timer, if there is a remaining non-empty skb */
 	if (ctx->tx_curr_skb != NULL && n > 0)

-- 
2.40.1.606.ga4b1b128d6-goog

Re: [PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize

From: Simon Horman <hidden>
Date: 2023-05-18 16:42:26

On Wed, May 17, 2023 at 01:38:08PM +0000, Tudor Ambarus wrote:

Currently in cdc_ncm_check_tx_max(), if dwNtbOutMaxSize is lower than
the calculated "min" value, but greater than zero, the logic sets
tx_max to dwNtbOutMaxSize. This is then used to allocate a new SKB in
cdc_ncm_fill_tx_frame() where all the data is handled.

For small values of dwNtbOutMaxSize the memory allocated during
alloc_skb(dwNtbOutMaxSize, GFP_ATOMIC) will have the same size, due to
how size is aligned at alloc time:
	size = SKB_DATA_ALIGN(size);
        size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
Thus we hit the same bug that we tried to squash with
commit 2be6d4d16a084 ("net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero")

Low values of dwNtbOutMaxSize do not cause an issue presently because at
alloc_skb() time more memory (512b) is allocated than required for the
SKB headers alone (320b), leaving some space (512b - 320b = 192b)
for CDC data (172b).

However, if more elements (for example 3 x u64 = [24b]) were added to
one of the SKB header structs, say 'struct skb_shared_info',
increasing its original size (320b [320b aligned]) to something larger
(344b [384b aligned]), then suddenly the CDC data (172b) no longer
fits in the spare SKB data area (512b - 384b = 128b).

Consequently the SKB bounds checking semantics fails and panics:

skbuff: skb_over_panic: text:ffffffff831f755b len:184 put:172 head:ffff88811f1c6c00 data:ffff88811f1c6c00 tail:0xb8 end:0x80 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:113!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 57 Comm: kworker/0:2 Not tainted 5.15.106-syzkaller-00249-g19c0ed55a470 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Workqueue: mld mld_ifc_work
RIP: 0010:skb_panic net/core/skbuff.c:113 [inline]
RIP: 0010:skb_over_panic+0x14c/0x150 net/core/skbuff.c:118
[snip]
Call Trace:
 <TASK>
 skb_put+0x151/0x210 net/core/skbuff.c:2047
 skb_put_zero include/linux/skbuff.h:2422 [inline]
 cdc_ncm_ndp16 drivers/net/usb/cdc_ncm.c:1131 [inline]
 cdc_ncm_fill_tx_frame+0x11ab/0x3da0 drivers/net/usb/cdc_ncm.c:1308
 cdc_ncm_tx_fixup+0xa3/0x100

Deal with too low values of dwNtbOutMaxSize, clamp it in the range
[USB_CDC_NCM_NTB_MIN_OUT_SIZE, CDC_NCM_NTB_MAX_SIZE_TX]. We ensure
enough data space is allocated to handle CDC data by making sure
dwNtbOutMaxSize is not smaller than USB_CDC_NCM_NTB_MIN_OUT_SIZE.

Fixes: 289507d3364f ("net: cdc_ncm: use sysfs for rx/tx aggregation tuning")
Cc: stable@vger.kernel.org
Reported-by: syzbot+9f575a1f15fc0c01ed69@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=b982f1059506db48409d
Link: https://lore.kernel.org/all/20211202143437.1411410-1-lee.jones@linaro.org/
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>

Reviewed-by: Simon Horman <redacted>

Re: [PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize

From: patchwork-bot+netdevbpf@kernel.org
Date: 2023-05-19 03:10:44

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski [off-list ref]:

On Wed, 17 May 2023 13:38:08 +0000 you wrote:

Currently in cdc_ncm_check_tx_max(), if dwNtbOutMaxSize is lower than
the calculated "min" value, but greater than zero, the logic sets
tx_max to dwNtbOutMaxSize. This is then used to allocate a new SKB in
cdc_ncm_fill_tx_frame() where all the data is handled.

For small values of dwNtbOutMaxSize the memory allocated during
alloc_skb(dwNtbOutMaxSize, GFP_ATOMIC) will have the same size, due to
how size is aligned at alloc time:
	size = SKB_DATA_ALIGN(size);
        size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
Thus we hit the same bug that we tried to squash with
commit 2be6d4d16a084 ("net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero")

[...]

Here is the summary with links:
  - net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize
    https://git.kernel.org/netdev/net/c/7e01c7f7046e

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

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