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authorSteven Rostedt <rostedt@goodmis.org>2010-11-08 23:20:27 -0500
committerJesse Barnes <jbarnes@virtuousgeek.org>2010-11-11 09:34:31 -0800
commitac3abf2c37a9b0be604ea9825705a8510a9a6ba3 (patch)
tree52cc5f8a785dc3890f20f46e6f514170d692ed6a
parentf6614b7bb405a9b35dd28baea989a749492c46b2 (diff)
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PCI hotplug: ibmphp: Add check to prevent reading beyond mapped area
While testing various randconfigs with ktest.pl, I hit the following panic: BUG: unable to handle kernel paging request at f7e54b03 IP: [<c0d63409>] ibmphp_access_ebda+0x101/0x19bb Adding printks, I found that the loop that reads the ebda blocks can move out of the mapped section. ibmphp_access_ebda: start=f7e44c00 size=5120 end=f7e46000 ibmphp_access_ebda: io_mem=f7e44d80 offset=384 ibmphp_access_ebda: io_mem=f7e54b03 offset=65283 The start of the iomap was at f7e44c00 and had a size of 5120, making the end f7e46000. We start with an offset of 0x180 or 384, giving the first read at 0xf7e44d80. Reading that location yields 65283, which is much bigger than the 5120 that was allocated and makes the next read at f7e54b03 which is outside the mapped area. Perhaps this is a bug in the driver, or buggy hardware, but this patch is more about not crashing my box on start up and just giving a warning if it detects this error. This patch at least lets my box boot with just a warning. Cc: Chandru Siddalingappa <chandru@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
-rw-r--r--drivers/pci/hotplug/ibmphp_ebda.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/pci/hotplug/ibmphp_ebda.c b/drivers/pci/hotplug/ibmphp_ebda.c
index 5becbdee402..2850e64deda 100644
--- a/drivers/pci/hotplug/ibmphp_ebda.c
+++ b/drivers/pci/hotplug/ibmphp_ebda.c
@@ -276,6 +276,12 @@ int __init ibmphp_access_ebda (void)
for (;;) {
offset = next_offset;
+
+ /* Make sure what we read is still in the mapped section */
+ if (WARN(offset > (ebda_sz * 1024 - 4),
+ "ibmphp_ebda: next read is beyond ebda_sz\n"))
+ break;
+
next_offset = readw (io_mem + offset); /* offset of next blk */
offset += 2;