From: Simon Horman <simon.horman@corigine.com>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: bjorn@mork.no, joneslee@google.com, oliver@neukum.org,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, linux-usb@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org,
syzbot+9f575a1f15fc0c01ed69@syzkaller.appspotmail.com
Subject: Re: [PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize
Date: Thu, 18 May 2023 18:42:11 +0200 [thread overview]
Message-ID: <ZGZVYx3k77Z3/9YQ@corigine.com> (raw)
In-Reply-To: <20230517133808.1873695-2-tudor.ambarus@linaro.org>
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 <simon.horman@corigine.com>
next prev parent reply other threads:[~2023-05-18 16:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-02 14:34 [PATCH 1/1] net: cdc_ncm: Allow for dwNtbOutMaxSize to be unset or zero Lee Jones
2021-12-03 1:51 ` Jakub Kicinski
2021-12-03 10:29 ` Bjørn Mork
2021-12-03 11:25 ` Lee Jones
2021-12-03 12:57 ` Bjørn Mork
2021-12-03 13:39 ` Lee Jones
2021-12-03 14:36 ` Bjørn Mork
2021-12-03 14:46 ` Lee Jones
2021-12-03 14:52 ` Bjørn Mork
2021-12-04 0:57 ` Jakub Kicinski
2023-05-17 13:38 ` [PATCH] net: cdc_ncm: Deal with too low values of dwNtbOutMaxSize Tudor Ambarus
2023-05-17 13:38 ` Tudor Ambarus
2023-05-18 16:42 ` Simon Horman [this message]
2023-05-19 3:10 ` patchwork-bot+netdevbpf
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