Message-ID: <EC7175BD-3814-4E66-AE6C-0B43E22A2635@oracle.com>
Date: Wed, 18 Sep 2024 22:55:31 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Dave Chinner <david@...morbit.com>,
        Trond Myklebust
	<trondmy@...merspace.com>
CC: syzbot <syzbot+6926ab9f6f7d7b50002e@...kaller.appspotmail.com>,
        Andrew
 Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List
	<linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        "muchun.song@...ux.dev" <muchun.song@...ux.dev>,
        "roman.gushchin@...ux.dev"
	<roman.gushchin@...ux.dev>,
        "syzkaller-bugs@...glegroups.com"
	<syzkaller-bugs@...glegroups.com>,
        "zhengqi.arch@...edance.com"
	<zhengqi.arch@...edance.com>,
        Linux NFS Mailing List
	<linux-nfs@...r.kernel.org>
Subject: Re: [syzbot] [mm?] KASAN: slab-use-after-free Read in shrinker_free



> On Sep 18, 2024, at 2:55 PM, Dave Chinner <david@...morbit.com> wrote:
> 
> On Wed, Sep 18, 2024 at 09:26:27AM -0700, syzbot wrote:
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    57719771a244 Merge tag 'sound-6.11' of git://git.kernel.or..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=122c17c7980000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=96be9a618e50f19f
>> dashboard link: https://syzkaller.appspot.com/bug?extid=6926ab9f6f7d7b50002e
>> 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=1559749f980000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1359749f980000
>> 
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/87498efcab61/disk-57719771.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/5703d19e746c/vmlinux-57719771.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/3744ba66862a/bzImage-57719771.xz
>> 
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+6926ab9f6f7d7b50002e@...kaller.appspotmail.com
>> 
>> svc: failed to register nfsdv3 RPC service (errno 512).
>> svc: failed to register nfsaclv3 RPC service (errno 512).
>> ==================================================================
>> BUG: KASAN: slab-use-after-free in shrinker_free+0x3b7/0x430 mm/shrinker.c:775
>> Read of size 4 at addr ffff8880206cbb1c by task syz-executor313/5320
>> 
>> CPU: 0 UID: 0 PID: 5320 Comm: syz-executor313 Not tainted 6.11.0-rc7-syzkaller-00145-g57719771a244 #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
>> Call Trace:
>> <TASK>
>> __dump_stack lib/dump_stack.c:93 [inline]
>> dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
>> print_address_description mm/kasan/report.c:377 [inline]
>> print_report+0xc3/0x620 mm/kasan/report.c:488
>> kasan_report+0xd9/0x110 mm/kasan/report.c:601
>> shrinker_free+0x3b7/0x430 mm/shrinker.c:775
>> nfsd_file_cache_shutdown+0xbc/0x480 fs/nfsd/filecache.c:891
>> nfsd_shutdown_generic fs/nfsd/nfssvc.c:329 [inline]
>> nfsd_shutdown_generic fs/nfsd/nfssvc.c:323 [inline]
>> nfsd_startup_net fs/nfsd/nfssvc.c:444 [inline]
>> nfsd_svc+0x6d4/0x970 fs/nfsd/nfssvc.c:817
>> nfsd_nl_threads_set_doit+0x52c/0xbc0 fs/nfsd/nfsctl.c:1714
> 
> This looks like an issue with nfsd startup error handling (maybe
> resulting in a double free?) and not a shrinker issue as such.
> CC'ing the NFS people.

This looks like a known problem that has presented with several
different failure modes. One of the latest reports:

https://lore.kernel.org/linux-nfs/adb93c51f6e34195716fd892049dc6e0f08b46aa.camel@kernel.org/

I can't think of any risk for doing what Jeff suggested here,
but I was hoping for some review by the author of 786615bc1ce8
("SUNRPC: If the rpcbind channel is disconnected, fail the call
to unregister").


>> genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
>> genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>> genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
>> netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2550
>> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>> netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
>> netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
>> sock_sendmsg_nosec net/socket.c:730 [inline]
>> __sock_sendmsg net/socket.c:745 [inline]
>> ____sys_sendmsg+0x9b4/0xb50 net/socket.c:2597
>> ___sys_sendmsg+0x135/0x1e0 net/socket.c:2651
>> __sys_sendmsg+0x117/0x1f0 net/socket.c:2680
>> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>> do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f51ae6e5ab9
>> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 1d 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
>> RSP: 002b:00007f51ae634158 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
>> RAX: ffffffffffffffda RBX: 00007f51ae768438 RCX: 00007f51ae6e5ab9
>> RDX: 0000000000000004 RSI: 0000000020000280 RDI: 0000000000000003
>> RBP: 00007f51ae768430 R08: 0000000000000008 R09: 0000000000000000
>> R10: 0000000000000003 R11: 0000000000000246 R12: 00007f51ae76843c
>> R13: 000000000000006e R14: 00007ffc1415e4a0 R15: 00007ffc1415e588
>> </TASK>
>> 
>> Allocated by task 5309:
>> kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>> kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>> poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
>> __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:387
>> kmalloc_noprof include/linux/slab.h:681 [inline]
>> kzalloc_noprof include/linux/slab.h:807 [inline]
>> shrinker_alloc+0xf8/0xb00 mm/shrinker.c:683
>> nfsd_file_cache_init+0x152/0x450 fs/nfsd/filecache.c:743
>> nfsd_startup_generic fs/nfsd/nfssvc.c:307 [inline]
>> nfsd_startup_net fs/nfsd/nfssvc.c:402 [inline]
>> nfsd_svc+0x542/0x970 fs/nfsd/nfssvc.c:817
>> nfsd_nl_threads_set_doit+0x52c/0xbc0 fs/nfsd/nfsctl.c:1714
>> genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
>> genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>> genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
>> netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2550
>> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>> netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
>> netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
>> sock_sendmsg_nosec net/socket.c:730 [inline]
>> __sock_sendmsg net/socket.c:745 [inline]
>> ____sys_sendmsg+0x9b4/0xb50 net/socket.c:2597
>> ___sys_sendmsg+0x135/0x1e0 net/socket.c:2651
>> __sys_sendmsg+0x117/0x1f0 net/socket.c:2680
>> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>> do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> 
>> Freed by task 0:
>> kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>> kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>> kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
>> poison_slab_object+0xf7/0x160 mm/kasan/common.c:240
>> __kasan_slab_free+0x32/0x50 mm/kasan/common.c:256
>> kasan_slab_free include/linux/kasan.h:184 [inline]
>> slab_free_hook mm/slub.c:2256 [inline]
>> slab_free mm/slub.c:4477 [inline]
>> kfree+0x12a/0x3b0 mm/slub.c:4598
>> rcu_do_batch kernel/rcu/tree.c:2569 [inline]
>> rcu_core+0x828/0x16b0 kernel/rcu/tree.c:2843
>> handle_softirqs+0x216/0x8f0 kernel/softirq.c:554
>> __do_softirq kernel/softirq.c:588 [inline]
>> invoke_softirq kernel/softirq.c:428 [inline]
>> __irq_exit_rcu kernel/softirq.c:637 [inline]
>> irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649
>> instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
>> sysvec_apic_timer_interrupt+0x95/0xb0 arch/x86/kernel/apic/apic.c:1043
>> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
>> 
>> Last potentially related work creation:
>> kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
>> __kasan_record_aux_stack+0xba/0xd0 mm/kasan/generic.c:541
>> __call_rcu_common.constprop.0+0x9a/0x790 kernel/rcu/tree.c:3106
>> shrinker_free+0xfe/0x430 mm/shrinker.c:807
>> nfsd_file_cache_shutdown+0xbc/0x480 fs/nfsd/filecache.c:891
>> nfsd_shutdown_generic fs/nfsd/nfssvc.c:329 [inline]
>> nfsd_shutdown_generic fs/nfsd/nfssvc.c:323 [inline]
>> nfsd_startup_net fs/nfsd/nfssvc.c:444 [inline]
>> nfsd_svc+0x6d4/0x970 fs/nfsd/nfssvc.c:817
>> nfsd_nl_threads_set_doit+0x52c/0xbc0 fs/nfsd/nfsctl.c:1714
>> genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
>> genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>> genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
>> netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2550
>> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>> netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>> netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
>> netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
>> sock_sendmsg_nosec net/socket.c:730 [inline]
>> __sock_sendmsg net/socket.c:745 [inline]
>> ____sys_sendmsg+0x9b4/0xb50 net/socket.c:2597
>> ___sys_sendmsg+0x135/0x1e0 net/socket.c:2651
>> __sys_sendmsg+0x117/0x1f0 net/socket.c:2680
>> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>> do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> 
>> The buggy address belongs to the object at ffff8880206cbb00
>> which belongs to the cache kmalloc-192 of size 192
>> The buggy address is located 28 bytes inside of
>> freed 192-byte region [ffff8880206cbb00, ffff8880206cbbc0)
>> 
>> The buggy address belongs to the physical page:
>> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x206cb
>> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
>> page_type: 0xfdffffff(slab)
>> raw: 00fff00000000000 ffff88801ac413c0 dead000000000100 dead000000000122
>> raw: 0000000000000000 0000000080100010 00000001fdffffff 0000000000000000
>> page dumped because: kasan: bad access detected
>> page_owner tracks the page as allocated
>> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 4560085887, free_ts 0
>> set_page_owner include/linux/page_owner.h:32 [inline]
>> post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1500
>> prep_new_page mm/page_alloc.c:1508 [inline]
>> get_page_from_freelist+0x1351/0x2e50 mm/page_alloc.c:3446
>> __alloc_pages_noprof+0x22b/0x2460 mm/page_alloc.c:4702
>> __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
>> alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
>> alloc_slab_page+0x4e/0xf0 mm/slub.c:2325
>> allocate_slab mm/slub.c:2488 [inline]
>> new_slab+0x84/0x260 mm/slub.c:2541
>> ___slab_alloc+0xdac/0x1870 mm/slub.c:3727
>> __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3817
>> __slab_alloc_node mm/slub.c:3870 [inline]
>> slab_alloc_node mm/slub.c:4029 [inline]
>> __kmalloc_cache_noprof+0x2c5/0x310 mm/slub.c:4188
>> kmalloc_noprof include/linux/slab.h:681 [inline]
>> kzalloc_noprof include/linux/slab.h:807 [inline]
>> call_usermodehelper_setup+0x9a/0x340 kernel/umh.c:363
>> kobject_uevent_env+0xde3/0x1670 lib/kobject_uevent.c:628
>> kset_register+0x1b6/0x2b0 lib/kobject.c:877
>> class_register+0x22e/0x340 drivers/base/class.c:203
>> typec_init+0x63/0x110 drivers/usb/typec/class.c:2518
>> do_one_initcall+0x128/0x630 init/main.c:1267
>> do_initcall_level init/main.c:1329 [inline]
>> do_initcalls init/main.c:1345 [inline]
>> do_basic_setup init/main.c:1364 [inline]
>> kernel_init_freeable+0x660/0xc50 init/main.c:1578
>> kernel_init+0x1c/0x2b0 init/main.c:1467
>> page_owner free stack trace missing
>> 
>> Memory state around the buggy address:
>> ffff8880206cba00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffff8880206cba80: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ffff8880206cbb00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                            ^
>> ffff8880206cbb80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>> ffff8880206cbc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ==================================================================
>> 
>> 
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@...glegroups.com.
>> 
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>> 
>> If the report is already addressed, let syzbot know by replying with:
>> #syz fix: exact-commit-title
>> 
>> If you want syzbot to run the reproducer, reply with:
>> #syz test: git://repo/address.git branch-or-commit-hash
>> If you attach or paste a git patch, syzbot will apply it before testing.
>> 
>> If you want to overwrite report's subsystems, reply with:
>> #syz set subsystems: new-subsystem
>> (See the list of subsystem names on the web dashboard)
>> 
>> If the report is a duplicate of another one, reply with:
>> #syz dup: exact-subject-of-another-report
>> 
>> If you want to undo deduplication, reply with:
>> #syz undup
>> 
> 
> -- 
> Dave Chinner
> david@...morbit.com

--
Chuck Lever

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