106 lines
3.9 KiB
Diff
106 lines
3.9 KiB
Diff
This patch adds poisoning and sanity checking to the RX DMA buffers.
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This is used for protection against buggy hardware/firmware that raises
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RX interrupts without doing an actual DMA transfer.
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This mechanism protects against rare "bad packets" (due to uninitialized skb data)
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and rare kernel crashes due to uninitialized RX headers.
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The poison is selected to not match on valid frames and to be cheap for checking.
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The poison check mechanism _might_ trigger incorrectly, if we are voluntarily
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receiving frames with bad PLCP headers. However, this is nonfatal, because the
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chance of such a match is basically zero and in case it happens it just results
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in dropping the packet.
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Bad-PLCP RX defaults to off, and you should leave it off unless you want to listen
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to the latest news broadcasted by your microwave oven.
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This patch also moves the initialization of the RX-header "length" field in front of
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the mapping of the DMA buffer. The CPU should not touch the buffer after we mapped it.
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Cc: stable@kernel.org
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Reported-by: Francesco Gringoli <francesco.gringoli@ing.unibs.it>
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Signed-off-by: Michael Buesch <mb@bu3sch.de>
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---
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Index: compat-wireless-2009-03-31/drivers/net/wireless/b43/dma.c
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===================================================================
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--- compat-wireless-2009-03-31.orig/drivers/net/wireless/b43/dma.c 2009-04-06 18:52:25.000000000 +0200
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+++ compat-wireless-2009-03-31/drivers/net/wireless/b43/dma.c 2009-04-06 18:52:30.000000000 +0200
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@@ -555,11 +555,32 @@ address_error:
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return 1;
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}
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+static bool b43_rx_buffer_is_poisoned(struct b43_dmaring *ring, struct sk_buff *skb)
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+{
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+ unsigned char *f = skb->data + ring->frameoffset;
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+
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+ return ((f[0] & f[1] & f[2] & f[3] & f[4] & f[5] & f[6] & f[7]) == 0xFF);
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+}
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+
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+static void b43_poison_rx_buffer(struct b43_dmaring *ring, struct sk_buff *skb)
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+{
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+ struct b43_rxhdr_fw4 *rxhdr;
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+ unsigned char *frame;
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+
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+ /* This poisons the RX buffer to detect DMA failures. */
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+
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+ rxhdr = (struct b43_rxhdr_fw4 *)(skb->data);
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+ rxhdr->frame_len = 0;
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+
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+ B43_WARN_ON(ring->rx_buffersize < ring->frameoffset + sizeof(struct b43_plcp_hdr6) + 2);
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+ frame = skb->data + ring->frameoffset;
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+ memset(frame, 0xFF, sizeof(struct b43_plcp_hdr6) + 2 /* padding */);
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+}
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+
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static int setup_rx_descbuffer(struct b43_dmaring *ring,
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struct b43_dmadesc_generic *desc,
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struct b43_dmadesc_meta *meta, gfp_t gfp_flags)
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{
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- struct b43_rxhdr_fw4 *rxhdr;
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dma_addr_t dmaaddr;
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struct sk_buff *skb;
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@@ -568,6 +589,7 @@ static int setup_rx_descbuffer(struct b4
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skb = __dev_alloc_skb(ring->rx_buffersize, gfp_flags);
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if (unlikely(!skb))
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return -ENOMEM;
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+ b43_poison_rx_buffer(ring, skb);
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dmaaddr = map_descbuffer(ring, skb->data, ring->rx_buffersize, 0);
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if (b43_dma_mapping_error(ring, dmaaddr, ring->rx_buffersize, 0)) {
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/* ugh. try to realloc in zone_dma */
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@@ -578,6 +600,7 @@ static int setup_rx_descbuffer(struct b4
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skb = __dev_alloc_skb(ring->rx_buffersize, gfp_flags);
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if (unlikely(!skb))
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return -ENOMEM;
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+ b43_poison_rx_buffer(ring, skb);
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dmaaddr = map_descbuffer(ring, skb->data,
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ring->rx_buffersize, 0);
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if (b43_dma_mapping_error(ring, dmaaddr, ring->rx_buffersize, 0)) {
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@@ -592,9 +615,6 @@ static int setup_rx_descbuffer(struct b4
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ring->ops->fill_descriptor(ring, desc, dmaaddr,
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ring->rx_buffersize, 0, 0, 0);
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- rxhdr = (struct b43_rxhdr_fw4 *)(skb->data);
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- rxhdr->frame_len = 0;
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-
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return 0;
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}
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@@ -1489,6 +1509,15 @@ static void dma_rx(struct b43_dmaring *r
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goto drop;
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}
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}
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+ if (unlikely(b43_rx_buffer_is_poisoned(ring, skb))) {
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+ /* Something went wrong with the DMA.
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+ * The device did not touch the buffer and did not overwrite the poison. */
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+ b43dbg(ring->dev->wl, "DMA RX: Dropping poisoned buffer.\n");
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+ /* recycle the descriptor buffer. */
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+ sync_descbuffer_for_device(ring, meta->dmaaddr,
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+ ring->rx_buffersize);
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+ goto drop;
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+ }
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if (unlikely(len > ring->rx_buffersize)) {
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/* The data did not fit into one descriptor buffer
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* and is split over multiple buffers.
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