openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

firewire: ohci: fix race in AR split packet handling 

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 <clemens@ladisch.de>
Cc: 2.6.22-2.6.36 <stable@kernel.org>
Tested-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Clemens Ladisch 2010-10-25 11:42:20 +02:00 committed by Stefan Richter
parent 85f7ffd5d2
commit a1f805e5e7
1 changed files with 21 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
drivers/firewire/ohci.c
View File

@ -750,20 +750,19 @@ 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);
@ -782,22 +781,30 @@ 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 =