linux-kernel - [PATCH 2/3] firewire: core: don't fail device creation in case of too large config ROM blocks

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Message-ID: <tkrat.040d1f77b4f1ddb4@s5r6.in-berlin.de>
Date:	Thu, 18 Feb 2010 01:52:45 +0100 (CET)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] firewire: core: don't fail device creation in case of too
 large config ROM blocks

It never happened yet, but better safe than sorry:  If a device's config
ROM contains a block which overlaps the boundary at 0xfffff00007ff, just
ignore that one block instead of refusing to add the device
representation.  That way, upper layers (kernelspace or userspace
drivers) might still be able to use the device to some degree.

That's better than total inaccessibility of the device.  Worse, the core
would have logged only a generic "giving up on config rom" message which
could only be debugged by feeding a firewire-ohci debug logging session
through a config ROM interpreter, IOW would likely remain undiagnosed.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/core-device.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

Index: linux-2.6.33-rc8/drivers/firewire/core-device.c
===================================================================
--- linux-2.6.33-rc8.orig/drivers/firewire/core-device.c
+++ linux-2.6.33-rc8/drivers/firewire/core-device.c
@@ -588,15 +588,19 @@ static int read_bus_info_block(struct fw
 		if (read_rom(device, generation, i, &rom[i]) != RCODE_COMPLETE)
 			goto out;
 		end = i + (rom[i] >> 16) + 1;
-		i++;
-		if (end > READ_BIB_ROM_SIZE)
+		if (end > READ_BIB_ROM_SIZE) {
 			/*
-			 * This block extends outside standard config
-			 * area (and the array we're reading it
-			 * into).  That's broken, so ignore this
-			 * device.
+			 * This block extends outside the config ROM which is
+			 * a firmware bug.  Ignore this whole block, i.e.
+			 * simply set a fake block length of 0.
 			 */
-			goto out;
+			fw_error("skipped invalid ROM block %x at %llx\n",
+				 rom[i],
+				 i * 4 | CSR_REGISTER_BASE | CSR_CONFIG_ROM);
+			rom[i] = 0;
+			end = i;
+		}
+		i++;
 
 		/*
 		 * Now read in the block.  If this is a directory

-- 
Stefan Richter
-=====-==-=- --=- =--=-
http://arcgraph.de/sr/

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