Re: FAILED: patch "[PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize" failed to apply to 4.14-stable tree

Hi!

In order to apply this without conflicts to 4.14-stable, one needs to apply a dependency, thus the sequence is:

7e01c7f7046e ("net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize") 0fa81b304a79 ("cdc_ncm: Implement the 32-bit version of NCM Transfer Block")

Let me know if you want me to send the patches explicitly. Cheers, ta

On 5/26/23 20:04, gregkh@linuxfoundation.org wrote:

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y git checkout FETCH_HEAD git cherry-pick -x 7e01c7f7046efc2c7c192c3619db43292b98e997 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023052625-mutual-punch-5c0b@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^..

Possible dependencies:

7e01c7f7046e ("net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize") 2be6d4d16a08 ("net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero") 0fa81b304a79 ("cdc_ncm: Implement the 32-bit version of NCM Transfer Block") 49c2c3f246e2 ("cdc_ncm: avoid padding beyond end of skb") 6314dab4b8fb ("net: cdc_ncm: GetNtbFormat endian fix")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7e01c7f7046efc2c7c192c3619db43292b98e997 Mon Sep 17 00:00:00 2001 From: Tudor Ambarus tudor.ambarus@linaro.org Date: Wed, 17 May 2023 13:38:08 +0000 Subject: [PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize

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 simon.horman@corigine.com Link: https://lore.kernel.org/r/20230517133808.1873695-2-tudor.ambarus@linaro.org Signed-off-by: Jakub Kicinski kuba@kernel.org

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)