Re: BISECTED: 'alloc_tag: populate memory for module tags as needed' crashes on boot.

From: Suren Baghdasaryan
Date: Fri Dec 06 2024 - 20:28:11 EST

On Fri, Dec 6, 2024 at 4:50 PM Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:
>
> On 12/6/24 16:15, Suren Baghdasaryan wrote:
> > On Fri, Dec 6, 2024 at 2:55 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> >>
> >> On Fri, Dec 6, 2024 at 2:43 PM Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:
> >>>
> >>> On 12/6/24 14:03, Suren Baghdasaryan wrote:
> >>>> On Fri, Dec 6, 2024 at 1:50 PM Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:
> >>>>>
> >>>>> Hello Suren,
> >>>>>
> >>>>> My system crashes on bootup, and I bisected to this commit.
> >>>>>
> >>>>> 0f9b685626daa2f8e19a9788625c9b624c223e45 is the first bad commit
> >>>>> commit 0f9b685626daa2f8e19a9788625c9b624c223e45
> >>>>> Author: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> >>>>> Date: Wed Oct 23 10:07:57 2024 -0700
> >>>>>
> >>>>> alloc_tag: populate memory for module tags as needed
> >>>>>
> >>>>> The memory reserved for module tags does not need to be backed by physical
> >>>>> pages until there are tags to store there. Change the way we reserve this
> >>>>> memory to allocate only virtual area for the tags and populate it with
> >>>>> physical pages as needed when we load a module.
> >>>>>
> >>>>> The crash looks like this:
> >>>>>
> >>>>> BUG: unable to handle page fault for address: fffffbfff4041000
> >>>>> #PF: supervisor read access in kernel mode
> >>>>> #PF: error_code(0x0000) - not-present page
> >>>>> PGD 44d0e7067 P4D 44d0e7067 PUD 44d0e3067 PMD 10bb38067 PTE 0
> >>>>> Oops: Oops: 0000 [#1] PREEMPT SMP KASAN
> >>>>> CPU: 0 UID: 0 PID: 319 Comm: systemd-udevd Not tainted 6.12.0-rc6+ #21
> >>>>> Hardware name: Default string Default string/SKYBAY, BIOS 5.12 02/15/2023
> >>>>> RIP: 0010:kasan_check_range+0xa5/0x190
> >>>>> Code: 8d 5a 07 4c 0f 49 da 49 c1 fb 03 45 85 db 0f 84 ce 00 00 00 45 89 db 4a 8d 14 d8 eb 0d 48 83 c0 08 48 39 d0 0f 84 b29
> >>>>> RSP: 0018:ffff88812c26f980 EFLAGS: 00010206
> >>>>> RAX: fffffbfff4041000 RBX: fffffbfff404101e RCX: ffffffff814ec29b
> >>>>> [ OK DX: fffffbfff4041018 RSI: 00000000000000f0 RDI: ffffffffa0208000
> >>>>> 0m] Finished BP: fffffbfff4041000 R08: 0000000000000001 R09: fffffbfff404101d
> >>>>> ;1;39msystemd-udR10: ffffffffa02080ef R11: 0000000000000003 R12: ffffffffa0208000
> >>>>> ev-trig…e R13: ffffc90000dac7c8 R14: ffffc90000dac7e8 R15: dffffc0000000000
> >>>>> - Coldplug All uFS: 00007fe869216b40(0000) GS:ffff88841da00000(0000) knlGS:0000000000000000
> >>>>> dev Devices.
> >>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>> CR2: fffffbfff4041000 CR3: 0000000121e86002 CR4: 00000000003706f0
> >>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>>>> Call Trace:
> >>>>> <TASK>
> >>>>> [ OK ? __die+0x1f/0x60
> >>>>> 0m] Reached targ ? page_fault_oops+0x258/0x910
> >>>>> et sysi ? dump_pagetable+0x690/0x690
> >>>>> nit.target - ? search_bpf_extables+0x22/0x250
> >>>>> System Initiali ? trace_page_fault_kernel+0x120/0x120
> >>>>> zation.
> >>>>> ? search_bpf_extables+0x164/0x250
> >>>>> ? kasan_check_range+0xa5/0x190
> >>>>> ? fixup_exception+0x4d/0xc70
> >>>>> ? exc_page_fault+0xe1/0xf0
> >>>>> [ OK ? asm_exc_page_fault+0x22/0x30
> >>>>> 0m] Reached targ ? load_module+0x3d7b/0x7560
> >>>>> et netw ? kasan_check_range+0xa5/0x190
> >>>>> ork.target - __asan_memcpy+0x38/0x60
> >>>>> Network.
> >>>>> load_module+0x3d7b/0x7560
> >>>>> ? module_frob_arch_sections+0x30/0x30
> >>>>> ? lockdep_lock+0xbe/0x1b0
> >>>>> ? rw_verify_area+0x18d/0x5e0
> >>>>> ? kernel_read_file+0x246/0x870
> >>>>> ? __x64_sys_fspick+0x290/0x290
> >>>>> ? init_module_from_file+0xd1/0x130
> >>>>> init_module_from_file+0xd1/0x130
> >>>>> ? __ia32_sys_init_module+0xa0/0xa0
> >>>>> ? lock_acquire+0x2d/0xb0
> >>>>> ? idempotent_init_module+0x116/0x790
> >>>>> ? do_raw_spin_unlock+0x54/0x220
> >>>>> idempotent_init_module+0x226/0x790
> >>>>> ? init_module_from_file+0x130/0x130
> >>>>> ? vm_mmap_pgoff+0x203/0x2e0
> >>>>> __x64_sys_finit_module+0xba/0x130
> >>>>> do_syscall_64+0x69/0x160
> >>>>> entry_SYSCALL_64_after_hwframe+0x4b/0x53
> >>>>> RIP: 0033:0x7fe869de327d
> >>>>> Code: 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 248
> >>>>> RSP: 002b:00007ffe34a828d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> >>>>> RAX: ffffffffffffffda RBX: 0000557fa8f3f3f0 RCX: 00007fe869de327d
> >>>>> RDX: 0000000000000000 RSI: 00007fe869f4943c RDI: 0000000000000006
> >>>>> RBP: 00007fe869f4943c R08: 0000000000000000 R09: 0000000000000000
> >>>>> R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000020000
> >>>>> R13: 0000557fa8f3f030 R14: 0000000000000000 R15: 0000557fa8f3d110
> >>>>> </TASK>
> >>>>> Modules linked in:
> >>>>> CR2: fffffbfff4041000
> >>>>> ---[ end trace 0000000000000000 ]---
> >>>>>
> >>>>> I suspect you only hit this with an unlucky amount of debugging enabled. The kernel config I used
> >>>>> is found here:
> >>>>>
> >>>>> http://www.candelatech.com/downloads/cfg-kasan-crash-regression.config
> >>>>>
> >>>>> I will be happy to test fixes.
> >>>>
> >>>> Hi Ben,
> >>>> Thanks for reporting the issue. Do you have these recent fixes in your tree:
> >>>>
> >>>> https://lore.kernel.org/all/20241130001423.1114965-1-surenb@xxxxxxxxxx/
> >>>> https://lore.kernel.org/all/20241205170528.81000-1-hao.ge@xxxxxxxxx/
> >>>>
> >>>> If not, couple you please apply them and see if the issue is still happening?
> >>>> Thanks,
> >>>> Suren.
> >>>
> >>> Hello Suren,
> >>>
> >>> Thanks for the quick response. The first patch is already in latest Linus tree,
> >
> > Hmm. Could you please double-check which tree you are using? I don't
> > see the first patch
> > (https://lore.kernel.org/all/20241130001423.1114965-1-surenb@xxxxxxxxxx/)
> > in Linus' tree. Maybe you are using linux-next?
>
> Sorry, you are correct. I must have mangled something when trying to apply
> the patch and I didn't look hard enough when patch said changes were already applied.
>
> I can re-test this next week...and for reference, kernel boots fine when you disable
> KASAN and other debugging.

Thanks! Please retest with this patch and let me know if you are still
having issues.
Suren.

>
> Thanks,
> Ben
>
>
> --
> Ben Greear <greearb@xxxxxxxxxxxxxxx>
> Candela Technologies Inc http://www.candelatech.com
>
>