On Sun, Nov 18, 2012 at 09:59:47AM -0500, Sasha Levin wrote: > On Sat, Nov 17, 2012 at 4:54 PM, Rafael Aquini <aquini@xxxxxxxxxx> wrote: > > On Sat, Nov 17, 2012 at 01:01:30PM -0500, Sasha Levin wrote: > >> > >> I'm getting the following while fuzzing using trinity inside a KVM tools guest, > >> on latest -next: > >> > >> [ 1642.783728] BUG: unable to handle kernel NULL pointer dereference at 0000000000000194 > >> [ 1642.785083] IP: [<ffffffff8122b354>] isolate_migratepages_range+0x344/0x7b0 > >> > >> My guess is that we see those because of a race during the check in > >> isolate_migratepages_range(). > >> > >> > >> Thanks, > >> Sasha > > > > Sasha, could you share your .config and steps you did used with trinity? So I > > can attempt to reproduce this issue you reported. > > Basically try running trinity (with ./trinity -m --quiet --dangerous > -l off) inside a disposable guest as root. > > I manage to hit that every couple of hours. > > Config attached. > Howdy Sasha, After several hours since last Sunday running trinity tests on a traditional KVM-QEMU guest as well as running it on a lkvm guest (both running next-20121115) I couldn't hit a single time the crash you've reported, (un)fortunately. Also, the .config you gave me, applied on top of next-20121115, haven't produced the same bin you've running and hitting the mentioned bug, apparently. Here's the RIP for your crash: [ 1642.783728] BUG: unable to handle kernel NULL pointer dereference at 0000000000000194 [ 1642.785083] IP: [<ffffffff8122b354>] isolate_migratepages_range+0x344/0x7b0 And here's the symbol address for the next-20121115 with your .config I've been running tests on: [raquini@x61 linux]$ nm -n vmlinux | grep isolate_migratepages_range ffffffff8122d890 T isolate_migratepages_range Also, it seems quite clear I'm missing something from your tree, as applying the RIP displacement (0x344) to my local isolate_migratepages_range sym addr leads me to the _middle_ of a instruction opcode that does not dereference any pointers at all. So, if you're consistently reproducing the same crash, consider to share with us a disassembled dump from the isolate_migratepages_range() you're running along with the crash stack-dump, please. Cheers! -- Rafael -- 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>