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Message-ID: <20241107142335.GB1172372@cmpxchg.org>
Date: Thu, 7 Nov 2024 09:23:35 -0500
From: Johannes Weiner <hannes@...xchg.org>
To: syzbot <syzbot+078be8bfa863cb9e0c6b@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, syzkaller-bugs@...glegroups.com,
Kairui Song <ryncsn@...il.com>
Subject: Re: [syzbot] [mm?] general protection fault in
swap_reclaim_full_clusters
On Tue, Nov 05, 2024 at 05:23:23PM -0800, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 59b723cd2adb Linux 6.12-rc6
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1076c740580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=b77c8a55ccf1d9e2
> dashboard link: https://syzkaller.appspot.com/bug?extid=078be8bfa863cb9e0c6b
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=167aa1f7980000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=110d86a7980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/699c7100a12a/disk-59b723cd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/74524a66d4bc/vmlinux-59b723cd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e81ed2bba0ef/bzImage-59b723cd.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+078be8bfa863cb9e0c6b@...kaller.appspotmail.com
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 1 UID: 0 PID: 51 Comm: kworker/1:1 Not tainted 6.12.0-rc6-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Workqueue: events swap_reclaim_work
> RIP: 0010:__list_del_entry_valid_or_report+0x20/0x1c0 lib/list_debug.c:49
> Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 83 c7 08 48 83 ec 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 01 00 00 48 89 f2 48 8b 4e 08 48 b8 00 00 00
> RSP: 0018:ffffc90000bb7c30 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88807b9ae078
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000001 R11: 000000000000004f R12: dffffc0000000000
> R13: ffffffffffffffb8 R14: ffff88807b9ae000 R15: ffffc90003af1000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fffaca68fb8 CR3: 00000000791c8000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> __list_del_entry_valid include/linux/list.h:124 [inline]
> __list_del_entry include/linux/list.h:215 [inline]
> list_move_tail include/linux/list.h:310 [inline]
> swap_reclaim_full_clusters+0x109/0x460 mm/swapfile.c:748
> swap_reclaim_work+0x2e/0x40 mm/swapfile.c:779
> process_one_work+0x958/0x1b30 kernel/workqueue.c:3229
> process_scheduled_works kernel/workqueue.c:3310 [inline]
> worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
> kthread+0x2c1/0x3a0 kernel/kthread.c:389
> ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__list_del_entry_valid_or_report+0x20/0x1c0 lib/list_debug.c:49
> Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 83 c7 08 48 83 ec 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 01 00 00 48 89 f2 48 8b 4e 08 48 b8 00 00 00
> RSP: 0018:ffffc90000bb7c30 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88807b9ae078
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000001 R11: 000000000000004f R12: dffffc0000000000
> R13: ffffffffffffffb8 R14: ffff88807b9ae000 R15: ffffc90003af1000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fffaca68fb8 CR3: 00000000791c8000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
> 0: 90 nop
> 1: 90 nop
> 2: 90 nop
> 3: 90 nop
> 4: 90 nop
> 5: 90 nop
> 6: 90 nop
> 7: 90 nop
> 8: 90 nop
> 9: 90 nop
> a: f3 0f 1e fa endbr64
> e: 48 89 fe mov %rdi,%rsi
> 11: 48 83 c7 08 add $0x8,%rdi
> 15: 48 83 ec 18 sub $0x18,%rsp
> 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 20: fc ff df
> 23: 48 89 fa mov %rdi,%rdx
> 26: 48 c1 ea 03 shr $0x3,%rdx
> * 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> 2e: 0f 85 19 01 00 00 jne 0x14d
> 34: 48 89 f2 mov %rsi,%rdx
> 37: 48 8b 4e 08 mov 0x8(%rsi),%rcx
> 3b: 48 rex.W
> 3c: b8 .byte 0xb8
> 3d: 00 00 add %al,(%rax)
>
>
This should fix it:
---
>From cf580e76e9fc23eab347e232b32d8bc9378a3f4e Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Thu, 7 Nov 2024 09:08:36 -0500
Subject: [PATCH] mm: swapfile: fix cluster reclaim work crash on rotational
devices
syzbot and Daan report a NULL pointer crash in the new full swap
cluster reclaim work:
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> CPU: 1 UID: 0 PID: 51 Comm: kworker/1:1 Not tainted 6.12.0-rc6-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Workqueue: events swap_reclaim_work
> RIP: 0010:__list_del_entry_valid_or_report+0x20/0x1c0 lib/list_debug.c:49
> Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 fe 48 83 c7 08 48 83 ec 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 01 00 00 48 89 f2 48 8b 4e 08 48 b8 00 00 00
> RSP: 0018:ffffc90000bb7c30 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88807b9ae078
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000001 R11: 000000000000004f R12: dffffc0000000000
> R13: ffffffffffffffb8 R14: ffff88807b9ae000 R15: ffffc90003af1000
> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fffaca68fb8 CR3: 00000000791c8000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> __list_del_entry_valid include/linux/list.h:124 [inline]
> __list_del_entry include/linux/list.h:215 [inline]
> list_move_tail include/linux/list.h:310 [inline]
> swap_reclaim_full_clusters+0x109/0x460 mm/swapfile.c:748
> swap_reclaim_work+0x2e/0x40 mm/swapfile.c:779
The syzbot console output indicates a virtual environment where
swapfile is on a rotational device. In this case, clusters aren't
actually used, and si->full_clusters is not initialized. Daan's report
is from qemu, so likely rotational too.
Make sure to only schedule the cluster reclaim work when clusters are
actually in use.
Link: https://lore.kernel.org/lkml/672ac50b.050a0220.2edce.1517.GAE@google.com/
Link: https://github.com/systemd/systemd/issues/35044
Fixes: 5168a68eb78f ("mm, swap: avoid over reclaim of full clusters")
Reported-by: syzbot+078be8bfa863cb9e0c6b@...kaller.appspotmail.com
Reported-by: Daan De Meyer <daan.j.demeyer@...il.com>
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
mm/swapfile.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 46bd4b1a3c07..9c85bd46ab7f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -929,7 +929,7 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
si->highest_bit = 0;
del_from_avail_list(si);
- if (vm_swap_full())
+ if (si->cluster_info && vm_swap_full())
schedule_work(&si->reclaim_work);
}
}
--
2.47.0
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