Joan Lledó, le lun. 07 févr. 2022 23:08:55 +0100, a ecrit: > > Samuel suggested on IRC that we could make it try the x86 map range > > function first > > and then fall back to hurd method, is there any problem with that? > > I don't have the time now to study it, but I'd say that would bypass the > protection set from the parent arbiter, since it would test the permissions > the current user has over "mem", before testing the permissions in the file > system created by the parent arbiter.
That is fine, since libpciaccess will notice that the user has no permissions over "mem". That being said, > Is there a way to detect, from the hurd_create() function, when is your > scenario running? > yes, it should use the x86 backend, but it calls > pci_system_x86_create() at [1], does that call fail in your scenario? His scenario is within the pci-arbiter, so !strcmp(netfs_server_name, "pci-arbiter") should be properly detecting it, and thus use the x86 backend, it's not expected that it doesn't happen so. I checked the code: 0x0806b40c <+28>: mov $0x81d606c,%eax (&netfs_server_name) 0x0806b412 <+34>: test %eax,%eax 0x0806b414 <+36>: je 0x806b437 <pci_system_hurd_create+71> 0x0806b416 <+38>: mov (%eax),%eax (netfs_server_name) 0x0806b418 <+40>: test %eax,%eax 0x0806b41a <+42>: je 0x806b437 <pci_system_hurd_create+71> 0x0806b41c <+44>: sub $0x8,%esp 0x0806b41f <+47>: lea -0x7077a(%ebx),%edx 0x0806b425 <+53>: push %edx 0x0806b426 <+54>: push %eax 0x0806b427 <+55>: call 0x8048270 (strcmp) 0x0806b42c <+60>: add $0x10,%esp 0x0806b42f <+63>: test %eax,%eax 0x0806b431 <+65>: je 0x806b568 <pci_system_hurd_create+376> (x86_create) 0x0806b437 <+71>: sub $0x8,%esp 0x0806b43a <+74>: push $0x1c 0x0806b43c <+76>: push $0x1 0x0806b43e <+78>: call 0x80aee30 <calloc> [etc.] (gdb) p &netfs_server_name $2 = (char **) 0x81d606c <netfs_server_name> (gdb) p netfs_server_name $1 = 0x81650ae "pci-arbiter" So it's properly accessing netfs_server_name. Possibly it's actually pci_system_x86_create that fails? Perhaps x86_enable_io()? Putting prints would help to make sure where things start to go unexpectedly. Samuel
