Re: FAILED: patch "[PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize" failed to apply to 4.19-stable tree

[Tudor Ambarus <tudor.ambarus@linaro.org>]

Hi!

In order to apply this without conflicts to 4.19-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 4.19-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-4.19.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 '2023052623-tricky-machinist-46c5@gregkh' --subject-prefix 'PATCH 4.19.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")
> 
> 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)
>