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

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Message-ID: <32f70816-1678-d6ab-0db1-6412ff7a7333@linux.dev>
Date: Wed, 23 Oct 2024 09:47:25 +0800
From: Hao Ge <hao.ge@...ux.dev>
To: Vlastimil Babka <vbabka@...e.cz>, Suren Baghdasaryan <surenb@...gle.com>,
 xiaopeitux@...mail.com
Cc: 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 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.

Best regards

Hao