linux-kernel - Re: [PATCH] slub/slub_kunit:fix a panic due to __kmalloc_cache

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Message-ID: <CAJuCfpHxrN_12h3pmK6Z+k7W1_6QWgAym9xgczcKTjYyLQ+S_Q@mail.gmail.com>
Date: Tue, 22 Oct 2024 18:58:02 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Hao Ge <hao.ge@...ux.dev>
Cc: Vlastimil Babka <vbabka@...e.cz>, xiaopeitux@...mail.com, akpm@...ux-foundation.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, yuzhao@...gle.com, 
	xiaopei01@...inos.cn, gehao@...inso.cn, xiongxin@...inos.cn
Subject: Re: [PATCH] slub/slub_kunit:fix a panic due to __kmalloc_cache_noprof
 incorretly use

On Tue, Oct 22, 2024 at 6:47 PM Hao Ge <hao.ge@...ux.dev> wrote:
>
>
> On 10/22/24 23:27, Vlastimil Babka wrote:
> > On 10/22/24 04:19, Hao Ge wrote:
> >> On 10/22/24 01:42, Suren Baghdasaryan wrote:
> >>> On Sun, Oct 20, 2024 at 11:59 PM <xiaopeitux@...mail.com> wrote:
> >>>> From: Pei Xiao <xiaopei01@...inos.cn>
> >>>>
> >>>> 'modprobe slub_kunit',will have a panic.The root cause is that
> >>>> __kmalloc_cache_noprof was directly ,which resulted in no alloc_tag
> >>>> being allocated.This caused current->alloc_tag to be null,leading to
> >>>> a null pointer dereference in alloc_tag_ref_set.
> >>> I think the root cause of this crash is the bug that is fixed by
> >>> https://lore.kernel.org/all/20241020070819.307944-1-hao.ge@linux.dev/.
> >>> Do you get this crash if you apply that fix?
> >> Yes, this patch has resolved the panic issue.
> >>>> Here is the log for the panic:
> >>>> [   74.779373][ T2158] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
> >>>> [   74.780130][ T2158] Mem abort info:
> >>>> [   74.780406][ T2158]   ESR = 0x0000000096000004
> >>>> [   74.780756][ T2158]   EC = 0x25: DABT (current EL), IL = 32 bits
> >>>> [   74.781225][ T2158]   SET = 0, FnV = 0
> >>>> [   74.781529][ T2158]   EA = 0, S1PTW = 0
> >>>> [   74.781836][ T2158]   FSC = 0x04: level 0 translation fault
> >>>> [   74.782288][ T2158] Data abort info:
> >>>> [   74.782577][ T2158]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
> >>>> [   74.783068][ T2158]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> >>>> [   74.783533][ T2158]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> >>>> [   74.784010][ T2158] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000105f34000
> >>>> [   74.784586][ T2158] [0000000000000020] pgd=0000000000000000, p4d=0000000000000000
> >>>> [   74.785293][ T2158] Internal error: Oops: 0000000096000004 [#1] SMP
> >>>> [   74.785805][ T2158] Modules linked in: slub_kunit kunit ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute ip6table_nat ip6table_mangle 4
> >>>> [   74.790661][ T2158] CPU: 0 UID: 0 PID: 2158 Comm: kunit_try_catch Kdump: loaded Tainted: G        W        N 6.12.0-rc3+ #2
> >>>> [   74.791535][ T2158] Tainted: [W]=WARN, [N]=TEST
> >>>> [   74.791889][ T2158] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> >>>> [   74.792479][ T2158] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> >>>> [   74.793101][ T2158] pc : alloc_tagging_slab_alloc_hook+0x120/0x270
> >>>> [   74.793607][ T2158] lr : alloc_tagging_slab_alloc_hook+0x120/0x270
> >>>>
> >>>> [   74.794095][ T2158] sp : ffff800084d33cd0
> >>>> [   74.794418][ T2158] x29: ffff800084d33cd0 x28: 0000000000000000 x27: 0000000000000000
> >>>> [   74.795095][ T2158] x26: 0000000000000000 x25: 0000000000000012 x24: ffff80007b30e314
> >>>> [   74.795822][ T2158] x23: ffff000390ff6f10 x22: 0000000000000000 x21: 0000000000000088
> >>>> [   74.796555][ T2158] x20: ffff000390285840 x19: fffffd7fc3ef7830 x18: ffffffffffffffff
> >>>> [   74.797283][ T2158] x17: ffff8000800e63b4 x16: ffff80007b33afc4 x15: ffff800081654c00
> >>>> [   74.798011][ T2158] x14: 0000000000000000 x13: 205d383531325420 x12: 5b5d383734363537
> >>>> [   74.798744][ T2158] x11: ffff800084d337e0 x10: 000000000000005d x9 : 00000000ffffffd0
> >>>> [   74.799476][ T2158] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008219d188 x6 : c0000000ffff7fff
> >>>> [   74.800206][ T2158] x5 : ffff0003fdbc9208 x4 : ffff800081edd188 x3 : 0000000000000001
> >>>> [   74.800932][ T2158] x2 : 0beaa6dee1ac5a00 x1 : 0beaa6dee1ac5a00 x0 : ffff80037c2cb000
> >>>> [   74.801656][ T2158] Call trace:
> >>>> [   74.801954][ T2158]  alloc_tagging_slab_alloc_hook+0x120/0x270
> >>>> [   74.802494][ T2158]  __kmalloc_cache_noprof+0x148/0x33c
> >>>> [   74.802976][ T2158]  test_kmalloc_redzone_access+0x4c/0x104 [slub_kunit]
> >>>> [   74.803607][ T2158]  kunit_try_run_case+0x70/0x17c [kunit]
> >>>> [   74.804124][ T2158]  kunit_generic_run_threadfn_adapter+0x2c/0x4c [kunit]
> >>>> [   74.804768][ T2158]  kthread+0x10c/0x118
> >>>> [   74.805141][ T2158]  ret_from_fork+0x10/0x20
> >>>> [   74.805540][ T2158] Code: b9400a80 11000400 b9000a80 97ffd858 (f94012d3)
> >>>> [   74.806176][ T2158] SMP: stopping secondary CPUs
> >>>> [   74.808130][ T2158] Starting crashdump kernel...
> >>>>
> >>> CC'ing Vlastimil.
> >>> This patch essentially reverts Vlastimil's "mm, slab: don't wrap
> >>> internal functions with alloc_hooks()" change. Please check why that
> >>> change was needed before proceeding.
> >>> If this change is indeed needed, please add:
> >> Hi Suren and Vlastimil
> >>
> >> In fact, besides the panic, there is also a warning here due to directly
> >> invoking__kmalloc_cache_noprof
> >>
> >> Regarding this, do you have any suggestions?
> >>
> >> [58162.947016] WARNING: CPU: 2 PID: 6210 at
> >> ./include/linux/alloc_tag.h:125 alloc_tagging_slab_alloc_hook+0x268/0x27c
> >> [58162.957721] Call trace:
> >> [58162.957919]  alloc_tagging_slab_alloc_hook+0x268/0x27c
> >> [58162.958286]  __kmalloc_cache_noprof+0x14c/0x344
> >> [58162.958615]  test_kmalloc_redzone_access+0x50/0x10c [slub_kunit]
> >> [58162.959045]  kunit_try_run_case+0x74/0x184 [kunit]
> >> [58162.959401]  kunit_generic_run_threadfn_adapter+0x2c/0x4c [kunit]
> >> [58162.959841]  kthread+0x10c/0x118
> >> [58162.960093]  ret_from_fork+0x10/0x20
> >> [58162.960363] ---[ end trace 0000000000000000 ]---
> > I see.
> > The kunit test is the only user of __kmalloc_cache_noprof outside of kmalloc()
> > itself so it's not worth defining again a wrapper for everyone, how about just
> > wrapping the two callsites?
> >
> > --- a/lib/slub_kunit.c
> > +++ b/lib/slub_kunit.c
> > @@ -141,7 +141,7 @@ static void test_kmalloc_redzone_access(struct kunit *test)
> >   {
> >          struct kmem_cache *s = test_kmem_cache_create("TestSlub_RZ_kmalloc", 32,
> >                                  SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE);
> > -       u8 *p = __kmalloc_cache_noprof(s, GFP_KERNEL, 18);
> > +       u8 *p = alloc_hooks(__kmalloc_cache_noprof(s, GFP_KERNEL, 18));
> >
> >          kasan_disable_current();
> >
> > @@ -199,7 +199,7 @@ static void test_krealloc_redzone_zeroing(struct kunit *test)
> >          struct kmem_cache *s = test_kmem_cache_create("TestSlub_krealloc", 64,
> >                                  SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE);
> >
> > -       p = __kmalloc_cache_noprof(s, GFP_KERNEL, 48);
> > +       p = alloc_hooks(__kmalloc_cache_noprof(s, GFP_KERNEL, 48));
> >          memset(p, 0xff, 48);
> >
> >          kasan_disable_current();
> >
> Hi  Vlastimil
>
> I agree with your point of view, thank you for you and Suren's help and
> suggestion.

That seems reasonable to me. Thanks!

>
> Best regards
>
> Hao
>