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Message-ID: <1b9a603d-fcc1-416f-bc90-c53af07d46d7@suse.cz>
Date: Fri, 18 Oct 2024 12:39:05 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: "yuan.gao" <yuan.gao@...oud.cn>, cl@...ux.com, penberg@...nel.org,
rientjes@...gle.com, iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
roman.gushchin@...ux.dev, 42.hyeyoo@...il.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mm/slub: Avoid list corruption when removing a slab
from the full list
On 10/18/24 08:44, yuan.gao wrote:
> Boot with slub_debug=UFPZ.
>
> If allocated object failed in alloc_consistency_checks, all objects of
> the slab will be marked as used, and then the slab will be removed from
> the partial list.
>
> When an object belonging to the slab got freed later, the remove_full()
> function is called. Because the slab is neither on the partial list nor
> on the full list, it eventually lead to a list corruption (actually a
> list poison being detected).
>
> So we need to mark and isolate the slab page with metadata corruption,
> do not put it back in circulation.
>
> Because the debug caches avoid all the fastpaths, reusing the frozen bit
> to mark slab page with metadata corruption seems to be fine.
>
> [ 4277.385669] list_del corruption, ffffea00044b3e50->next is LIST_POISON1 (dead000000000100)
> [ 4277.387023] ------------[ cut here ]------------
> [ 4277.387880] kernel BUG at lib/list_debug.c:56!
> [ 4277.388680] invalid opcode: 0000 [#1] PREEMPT SMP PTI
> [ 4277.389562] CPU: 5 PID: 90 Comm: kworker/5:1 Kdump: loaded Tainted: G OE 6.6.1-1 #1
> [ 4277.392113] Workqueue: xfs-inodegc/vda1 xfs_inodegc_worker [xfs]
> [ 4277.393551] RIP: 0010:__list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.394518] Code: 48 91 82 e8 37 f9 9a ff 0f 0b 48 89 fe 48 c7 c7 28 49 91 82 e8 26 f9 9a ff 0f 0b 48 89 fe 48 c7 c7 58 49 91
> [ 4277.397292] RSP: 0018:ffffc90000333b38 EFLAGS: 00010082
> [ 4277.398202] RAX: 000000000000004e RBX: ffffea00044b3e50 RCX: 0000000000000000
> [ 4277.399340] RDX: 0000000000000002 RSI: ffffffff828f8715 RDI: 00000000ffffffff
> [ 4277.400545] RBP: ffffea00044b3e40 R08: 0000000000000000 R09: ffffc900003339f0
> [ 4277.401710] R10: 0000000000000003 R11: ffffffff82d44088 R12: ffff888112cf9910
> [ 4277.402887] R13: 0000000000000001 R14: 0000000000000001 R15: ffff8881000424c0
> [ 4277.404049] FS: 0000000000000000(0000) GS:ffff88842fd40000(0000) knlGS:0000000000000000
> [ 4277.405357] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 4277.406389] CR2: 00007f2ad0b24000 CR3: 0000000102a3a006 CR4: 00000000007706e0
> [ 4277.407589] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 4277.408780] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 4277.410000] PKRU: 55555554
> [ 4277.410645] Call Trace:
> [ 4277.411234] <TASK>
> [ 4277.411777] ? die+0x32/0x80
> [ 4277.412439] ? do_trap+0xd6/0x100
> [ 4277.413150] ? __list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.414158] ? do_error_trap+0x6a/0x90
> [ 4277.414948] ? __list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.415915] ? exc_invalid_op+0x4c/0x60
> [ 4277.416710] ? __list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.417675] ? asm_exc_invalid_op+0x16/0x20
> [ 4277.418482] ? __list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.419466] ? __list_del_entry_valid_or_report+0x7b/0xc0
> [ 4277.420410] free_to_partial_list+0x515/0x5e0
> [ 4277.421242] ? xfs_iext_remove+0x41a/0xa10 [xfs]
> [ 4277.422298] xfs_iext_remove+0x41a/0xa10 [xfs]
> [ 4277.423316] ? xfs_inodegc_worker+0xb4/0x1a0 [xfs]
> [ 4277.424383] xfs_bmap_del_extent_delay+0x4fe/0x7d0 [xfs]
> [ 4277.425490] __xfs_bunmapi+0x50d/0x840 [xfs]
> [ 4277.426445] xfs_itruncate_extents_flags+0x13a/0x490 [xfs]
> [ 4277.427553] xfs_inactive_truncate+0xa3/0x120 [xfs]
> [ 4277.428567] xfs_inactive+0x22d/0x290 [xfs]
> [ 4277.429500] xfs_inodegc_worker+0xb4/0x1a0 [xfs]
> [ 4277.430479] process_one_work+0x171/0x340
> [ 4277.431227] worker_thread+0x277/0x390
> [ 4277.431962] ? __pfx_worker_thread+0x10/0x10
> [ 4277.432752] kthread+0xf0/0x120
> [ 4277.433382] ? __pfx_kthread+0x10/0x10
> [ 4277.434134] ret_from_fork+0x2d/0x50
> [ 4277.434837] ? __pfx_kthread+0x10/0x10
> [ 4277.435566] ret_from_fork_asm+0x1b/0x30
> [ 4277.436280] </TASK>
>
> v4:
> - Rephrase wording.
> - Remove a useless add_full().
>
> v3:
> - Reuse slab->fronzen bit as a corrupted marker.
> - https://lore.kernel.org/all/20241011102020.58087-1-yuan.gao@ucloud.cn/
>
> v2:
> - Call remove_partial() and add_full() only for slab folios.
> - https://lore.kernel.org/linux-mm/20241007091850.16959-1-yuan.gao@ucloud.cn/
>
> v1:
> - https://lore.kernel.org/linux-mm/20241006044755.79634-1-yuan.gao@ucloud.cn/
>
> Signed-off-by: yuan.gao <yuan.gao@...oud.cn>
> Fixes: 643b113849d8 ("slub: enable tracking of full slabs")
> Suggested-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Applied, thanks!
> ---
> mm/slab.h | 5 +++++
> mm/slub.c | 9 ++++++++-
> 2 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 6c6fe6d630ce..8d7caf50ef96 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -73,6 +73,11 @@ struct slab {
> struct {
> unsigned inuse:16;
> unsigned objects:15;
> + /*
> + * If slab debugging is enabled then the
> + * frozen bit can be reused to indicate
> + * that the slab was corrupted
> + */
> unsigned frozen:1;
> };
> };
> diff --git a/mm/slub.c b/mm/slub.c
> index 5b832512044e..15ba89fef89a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1423,6 +1423,11 @@ static int check_slab(struct kmem_cache *s, struct slab *slab)
> slab->inuse, slab->objects);
> return 0;
> }
> + if (slab->frozen) {
> + slab_err(s, slab, "Slab disabled since SLUB metadata consistency check failed");
> + return 0;
> + }
> +
> /* Slab_pad_check fixes things up after itself */
> slab_pad_check(s, slab);
> return 1;
> @@ -1603,6 +1608,7 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s,
> slab_fix(s, "Marking all objects used");
> slab->inuse = slab->objects;
> slab->freelist = NULL;
> + slab->frozen = 1; /* mark consistency-failed slab as frozen */
> }
> return false;
> }
> @@ -2744,7 +2750,8 @@ static void *alloc_single_from_partial(struct kmem_cache *s,
> slab->inuse++;
>
> if (!alloc_debug_processing(s, slab, object, orig_size)) {
> - remove_partial(n, slab);
> + if (folio_test_slab(slab_folio(slab)))
> + remove_partial(n, slab);
> return NULL;
> }
>
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