On Sat, May 14, 2016 at 12:07:44PM +0200, Martin Mares wrote: > Hello! > > > I have been using lspci (v3.2.1) on Centos 7.2 to find out why a LSI 9420-4i > > raid controller did not work with the linux driver but when I used lspci > > with the -vv option as root the machine locked up completely and even the > > reset button did not work. lspci v3.4.1 does the same. > > As I was curious as to the reason why this could happen I compiled and ran > > it under gdb and found that the cap_vpd() function caused the problem. The > > raid card said that it supported vpd but the first call of read_vpd() > > returned a value of FFh for the variable "tag" and the next call of > > read_vpd() would hang the pc. > > I added code to return from the function after the first read_vpd but when > > the subsequent capability structures were read the values were different > > from those previously dumped using the -xxx option and lspci would crash as > > it followed the modified linked list off into oblivion. > > I commented out the call to cap_vpd() and it worked correctly and I could > > then see all the capability details. > > > > I would like to make a request that the call to cap_vpd be disabled by > > default and enabled by a command line parameter if necessary as it is very > > likely that it is the cause of problems with the -vv and -vvv options. As > > this incident has shown, the consequences of reading the vpd can be very > > dangerous. > > It smells of faulty hardware. Reading the VPD should not have any side > effects. > > It seems to be a rather singular problem (your report was the first one > I received since we added dumping of VPD in 2009) and it is not limited > to lspci anyway -- other programs could crash your system by accessing > the particular file in sysfs. > > I would recommend blacklisting your device in the kernel, so that VPD > will not be provided by sysfs at all. We do have some devices blacklisted in the kernel, including several LSI devices. This commit appeared in v4.6: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7c20078a8197 Based on the v4.6-rc6 dmesg log you (martinman3) attached at https://bugs.centos.org/view.php?id=10818, I think your LSI 9420-4i device is "pci 0000:05:00.0: [1000:0073]". v4.6-rc6 includes 7c20078a8197, and [1000:0073] is included in that blacklist. Did you still see the system hang with v4.6-rc6? If so, we still have work to do. The blacklist should make it safe to dump the VPD via sysfs, e.g., # xxd /sys/devices/pci0000:00/0000:00:05:00.0/vpd You shouldn't see any VPD data, and the machine should not hang. I don't know whether lspci reads VPD using sysfs or a different way. If it reads it differently, it's possible it could still cause a hang, even with the kernel blacklist. But at the hardware level, reading VPD requires access to two registers on the device, and I don't think that can be done safely without kernel support, so I hope lspci is using sysfs. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
