From 55b3b58713f2152ac92d8bb108a9561ac47f74bf Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Mon, 25 Oct 2010 11:42:20 +0200 Subject: [PATCH] firewire: ohci: fix race in AR split packet handling commit a1f805e5e73a8fe166b71c6592d3837df0cd5e2e upstream. When handling an AR buffer that has been completely filled, we assumed that its descriptor will not be read by the controller and can be overwritten. However, when the last received packet happens to end at the end of the buffer, the controller might not yet have moved on to the next buffer and might read the branch address later. If we overwrite and free the page before that, the DMA context will either go dead because of an invalid Z value, or go off into some random memory. To fix this, ensure that the descriptor does not get overwritten by using only the actual buffer instead of the entire page for reassembling the split packet. Furthermore, to avoid freeing the page too early, move on to the next buffer only when some data in it guarantees that the controller has moved on. This should eliminate the remaining firewire-net problems. Signed-off-by: Clemens Ladisch Tested-by: Maxim Levitsky Signed-off-by: Stefan Richter Signed-off-by: Paul Gortmaker --- drivers/firewire/ohci.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c index b1b0281551e3..38168893aba2 100644 --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -647,20 +647,19 @@ static void ar_context_tasklet(unsigned long data) */ offset = offsetof(struct ar_buffer, data); - start = buffer = ab; + start = ab; start_bus = le32_to_cpu(ab->descriptor.data_address) - offset; + buffer = ab->data; ab = ab->next; d = &ab->descriptor; - size = buffer + PAGE_SIZE - ctx->pointer; + size = start + PAGE_SIZE - ctx->pointer; /* valid buffer data in the next page */ rest = le16_to_cpu(d->req_count) - le16_to_cpu(d->res_count); /* what actually fits in this page */ - size2 = min(rest, (size_t)PAGE_SIZE - size); + size2 = min(rest, (size_t)PAGE_SIZE - offset - size); memmove(buffer, ctx->pointer, size); memcpy(buffer + size, ab->data, size2); - ctx->current_buffer = ab; - ctx->pointer = (void *) ab->data + rest; while (size > 0) { void *next = handle_ar_packet(ctx, buffer); @@ -679,22 +678,30 @@ static void ar_context_tasklet(unsigned long data) size -= pktsize; /* fill up this page again */ size3 = min(rest - size2, - (size_t)PAGE_SIZE - size - size2); + (size_t)PAGE_SIZE - offset - size - size2); memcpy(buffer + size + size2, (void *) ab->data + size2, size3); size2 += size3; } - /* handle the packets that are fully in the next page */ - buffer = (void *) ab->data + (buffer - (start + size)); - end = (void *) ab->data + rest; + if (rest > 0) { + /* handle the packets that are fully in the next page */ + buffer = (void *) ab->data + + (buffer - (start + offset + size)); + end = (void *) ab->data + rest; - while (buffer < end) - buffer = handle_ar_packet(ctx, buffer); + while (buffer < end) + buffer = handle_ar_packet(ctx, buffer); - dma_free_coherent(ohci->card.device, PAGE_SIZE, - start, start_bus); - ar_context_add_page(ctx); + ctx->current_buffer = ab; + ctx->pointer = end; + + dma_free_coherent(ohci->card.device, PAGE_SIZE, + start, start_bus); + ar_context_add_page(ctx); + } else { + ctx->pointer = start + PAGE_SIZE; + } } else { buffer = ctx->pointer; ctx->pointer = end = -- 2.39.5