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.
