On Sat, Mar 23, 2024 at 8:52 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Sat, Mar 23, 2024 at 5:50 PM Andrei Matei <andreimatei1@xxxxxxxxx> wrote: > > > > + Edward > > > > On Thu, Mar 21, 2024 at 3:33 AM Alexei Starovoitov > > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > > > Hi Andrei, > > > > > > looks like the refactoring of stack access introduced a bug. > > > See the reproducer below. > > > positive offsets are not caught by check_stack_access_within_bounds(). > > > > check_stack_access_within_bounds() tries to catch positive offsets; > > It does: [1] > > > > err = check_stack_slot_within_bounds(env, min_off, state, type); > > if (!err && max_off > 0) > > err = -EINVAL; /* out of stack access into non-negative offsets */ > > > > Notice the max_off > 0 in there. > > And we have various tests that seem to check that positive offsets are > > rejected. Do you know what the bug is? > > I'm thinking maybe there's some overflow going on, except that UBSAN > > reported an index of -1 as being the problem. > > > > Edward, I see that you've been tickling the robot trying to narrow the issue; > > perhaps you've figured it out? > > > > If the bug is not immediately apparent to anyone, I would really appreciate a > > bit of tutoring around how to reproduce and get verifier logs. > > The repro is right there in the email I forwarded: > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15c38711180000 I understand, but how does one go from this to either BPF assembly, or to running it in such a way that you also get verifier logs?
