> On Sep 1, 2022, at 9:51 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > > On Tue, Aug 30, 2022 at 1:49 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote: >> >> On Tue, 2022-08-30 at 13:14 -0400, Olga Kornievskaia wrote: >>> Hi folks, >>> >>> Is this a known nfsd kernel oops in 6.0-rc1. Was running xfstests on >>> pre-rhel-9.1 client against 6.0-rc1 server when it panic-ed. >>> >>> [ 5554.769159] BUG: KASAN: null-ptr-deref in kernel_sendpage+0x60/0x220 >>> [ 5554.770526] Read of size 8 at addr 0000000000000008 by task nfsd/2590 >>> [ 5554.771899] >> >> No, I haven't seen this one. I'm guessing the page pointer passed to >> kernel_sendpage was probably NULL, so this may be a case where something >> walked off the end of the rq_pages array? >> >> Beyond that I can't tell much from just this stack trace. It might be >> nice to see what line of code kernel_sendpage+0x60 refers to on your >> kernel. > > After getting debug symbols this is what gdb told me... > > (gdb) l *(kernel_sendpage+0x60) > 0xffffffff81cbd570 is in kernel_sendpage (./include/linux/page-flags.h:487). > 482 TESTCLEARFLAG(LRU, lru, PF_HEAD) > 483 PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD) > 484 TESTCLEARFLAG(Active, active, PF_HEAD) > 485 PAGEFLAG(Workingset, workingset, PF_HEAD) > 486 TESTCLEARFLAG(Workingset, workingset, PF_HEAD) > 487 __PAGEFLAG(Slab, slab, PF_NO_TAIL) > 488 __PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL) > 489 PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */ > 490 > 491 /* Xen */ > > I'm unable to complete a git bisect. Could somebody suggest what to do > when a git bisect midpoint results in an unbootable kernel? I can't > "skip" this point can I? I'm not sure if marking it "bad" makes sense > since it's not relevant to the actual problem. Try skipping. I think "git bisect" is supposed to be smart enough to figure things out after a skip. If not, start over and pick endpoints that you think might avoid the unbootable kernels. Even adjusting one endpoint a little might be enough to make bisect pick new targets that avoid the unbootable kernels. -- Chuck Lever
