Search Linux Wireless

Re: [PATCH 6/6] ath10k: sdio: replace skb_trim with explicit set of skb->len

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 4/12/19 3:17 PM, Kalle Valo wrote:
Erik Stromdahl <erik.stromdahl@xxxxxxxxx> writes:

This patch fixes a bug with padding of the skb data buffer.
Since skb_trim can only be used to reduce the skb len, it is useless when
we pad (increase the length of) the skb. Instead we must set skb->len
directly.

Signed-off-by: Erik Stromdahl <erik.stromdahl@xxxxxxxxx>
---
  drivers/net/wireless/ath/ath10k/sdio.c | 7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
index 3eb241cb8a25..989e3f563f3d 100644
--- a/drivers/net/wireless/ath/ath10k/sdio.c
+++ b/drivers/net/wireless/ath/ath10k/sdio.c
@@ -1496,7 +1496,12 @@ static int ath10k_sdio_hif_tx_sg(struct ath10k *ar, u8 pipe_id,
  		skb = items[i].transfer_context;
  		padded_len = ath10k_sdio_calc_txrx_padded_len(ar_sdio,
  							      skb->len);
-		skb_trim(skb, padded_len);
+		/* FIXME: unsure if just extending the skb len is the right
+		 * thing to do since we might read outside the skb->data
+		 * buffer. But we really don't want to realloc the skb just to
+		 * pad the length.
+		 */
+		skb->len = padded_len;

Good catch! But I don't think you can modify skb->len directly like
that. There is skb_pad() but that doesn't change skb->len, so that most
likely needs more changes. So maybe skb_put() is the safest here?

I have tried a few different solutions for this, but none seems to be
bullet proof.

skb_pad() raises a BUG() if there is not enough space in skb->data.

The best candidate so far has been skb_put_padto(). It pads and reallocates
the skb if needed.

The problem is that it also cause a panic if there is more than one reference
to the skb (skb_shared() returns true).

Some of the management frames via nl80211 have a refcount of 2.
In this case it is not possible to free and allocate the skb since there are
other users/references.

I think I will have to make some kind of solution where I copy the content of
the skb to an internal buffer instead.



[Index of Archives]     [Linux Host AP]     [ATH6KL]     [Linux Wireless Personal Area Network]     [Linux Bluetooth]     [Wireless Regulations]     [Linux Netdev]     [Kernel Newbies]     [Linux Kernel]     [IDE]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite Hiking]     [MIPS Linux]     [ARM Linux]     [Linux RAID]

  Powered by Linux