On 06/13/2014 12:13 AM, Dave Jones wrote: > On Fri, Jun 13, 2014 at 12:01:37AM -0400, Sasha Levin wrote: > > On 06/12/2014 11:27 PM, Dan Aloni wrote: > > > On Thu, Jun 12, 2014 at 10:56:16PM -0400, Sasha Levin wrote: > > >> > Hi all, > > >> > > > >> > Okay, I'm really lost. I got the following when fuzzing, and can't really explain what's > > >> > going on. It seems that we get a "unable to handle kernel paging request" when running > > >> > rather simple code, and I can't figure out how it would cause it. > > > [..] > > >> > Which agrees with the trace I got: > > >> > > > >> > [ 516.309720] BUG: unable to handle kernel paging request at ffffffffa0f12560 > > >> > [ 516.309720] IP: netlink_getsockopt (net/netlink/af_netlink.c:2271) > > > [..] > > >> > [ 516.309720] RIP netlink_getsockopt (net/netlink/af_netlink.c:2271) > > >> > [ 516.309720] RSP <ffff8803fc85fed8> > > >> > [ 516.309720] CR2: ffffffffa0f12560 > > >> > > > >> > They only theory I had so far is that netlink is a module, and has gone away while the code > > >> > was executing, but netlink isn't a module on my kernel. > > > The RIP - 0xffffffffa0f12560 is in the range (from Documentation/x86/x86_64/mm.txt): > > > > > > ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space > > > > > > So seems it was in a module. > > > > Yup, that's why that theory came up, but when I checked my config: > > ... > > that theory went away. (also confirmed by not finding a netlink module.) > > > > What about the kernel .text overflowing into the modules space? The loader > > checks for that, but can something like that happen after everything is > > up and running? I'll look into that tomorrow. > > another theory: Trinity can sometimes generate plausible looking module > addresses and pass those in structs etc. > > I wonder if there's somewhere in that path that isn't checking that the address > in the optval it got is actually a userspace address before it tries to write to it. It happened again, and this time I've left the kernel addresses in, and it's quite interesting: [ 88.837926] Call Trace: [ 88.837926] [<ffffffff9ff6a792>] __sock_create+0x292/0x3c0 [ 88.837926] [<ffffffff9ff6a610>] ? __sock_create+0x110/0x3c0 [ 88.837926] [<ffffffff9ff6a920>] sock_create+0x30/0x40 [ 88.837926] [<ffffffff9ff6ad4c>] SyS_socket+0x2c/0x70 [ 88.837926] [<ffffffffa0561c30>] ? tracesys+0x7e/0xe6 [ 88.837926] [<ffffffffa0561c93>] tracesys+0xe1/0xe6 tracesys() seems to live inside a module space here? Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>