Received-SPF: pass (google.com: best guess record for domain of linux-nfs-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Fri, 20 Mar 2020 20:51:20 -0600
Message-ID: <CAHmME9ro8BPBTMfu8dEbGmkH7qHLdQ=CXGEOW2C7MR4bmT6T+w@mail.gmail.com>
Subject: refcount underflow in nfsd41_destroy_cb
To:     linux-nfs@vger.kernel.org
Cc:     Jan Psota <jasiu@belsznica.pl>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-nfs-owner@vger.kernel.org
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Hello,

A user erroneously sent me a refcount UaF in NFS with 5.6-rc6. I
thought I should forward it onward here in case this is not already
known. The original reporter is CC'd in case you have any questions.

Regards,
Jason

-------8<------------------------

Mar 20 21:43:34 agro kernel: ------------[ cut here ]------------
Mar 20 21:43:34 agro kernel: refcount_t: underflow; use-after-free.
Mar 20 21:43:34 agro kernel: WARNING: CPU: 1 PID: 9334 at
lib/refcount.c:28 refcount_warn_saturate+0xd9/0xe0
Mar 20 21:43:34 agro kernel: Modules linked in: md5 wireguard
curve25519_x86_64 libcurve25519_generic libchacha20poly1305
chacha_x86_64 libchacha poly1305_x86_64 ip6_udp_tunnel udp_tunnel
libblake2s blake2s_x86_64 libblake2s_generic xt_mac xt_nat
xt_MASQUERADE xt_REDIRECT xt_owner xt_comment ipt_REJECT
nf_reject_ipv4 xt_mark xt_hashlimit xt_multiport nfnetlink_log
xt_NFLOG nf_log_ipv4 nf_log_common xt_LOG nf_nat_tftp nf_nat_sip
nf_nat_h323 nf_nat_ftp nf_conntrack_tftp nf_conntrack_sip
nf_conntrack_netlink nfnetlink nf_conntrack_h323 nf_conntrack_ftp nfsd
auth_rpcgss nfs_acl lockd grace sunrpc cpufreq_ondemand msr bridge stp
llc xt_tcpudp xt_conntrack iptable_mangle iptable_nat nf_nat
nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 iptable_raw iptable_filter
ip_tables x_tables btrfs blake2b_generic xor raid6_pq libcrc32c
zstd_compress zstd_decompress zlib_deflate zlib_inflate uas
usb_storage snd_hda_codec_realtek snd_hda_codec_generic matroxfb_base
matroxfb_g450 matroxfb_Ti3026 snd_hda_int
 el matroxfb_accel
Mar 20 21:43:34 agro kernel:  snd_intel_dspcfg cfbfillrect cfbimgblt
atlantic snd_hda_codec r8169 cfbcopyarea e1000e snd_hda_core snd_hwdep
matroxfb_DAC1064 g450_pll matroxfb_misc ptp realtek fb snd_pcm libphy
snd_timer mxm_wmi xhci_pci pcspkr i2c_piix4 input_leds pps_core fbdev
k10temp ohci_pci snd xhci_hcd ohci_hcd ehci_pci soundcore i2c_core
ehci_hcd wmi acpi_cpufreq vhci_hcd usbip_core usbcore usb_common
vhost_net vhost kvm_amd kvm irqbypass loop tun fuse it87 hwmon_vid
hwmon
Mar 20 21:43:34 agro kernel: CPU: 1 PID: 9334 Comm: kworker/u16:3 Not
tainted 5.6.0-rc6 #1
Mar 20 21:43:34 agro kernel: Hardware name: Gigabyte Technology Co.,
Ltd. GA-990FXA-UD5/GA-990FXA-UD5, BIOS F12 10/03/2013
Mar 20 21:43:34 agro kernel: Workqueue: rpciod rpc_async_schedule [sunrpc]
Mar 20 21:43:34 agro kernel: RIP: 0010:refcount_warn_saturate+0xd9/0xe0
Mar 20 21:43:34 agro kernel: Code: ff 48 c7 c7 e8 ff d5 81 c6 05 cd 49
b5 00 01 e8 4d 04 cf ff 0f 0b c3 48 c7 c7 90 ff d5 81 c6 05 b9 49 b5
00 01 e8 37 04 cf ff <0f> 0b c3 0f 1f 40 00 8b 07 3d 00 00 00 c0 74 12
83 f8 01 74 46 8d
Mar 20 21:43:34 agro kernel: RSP: 0018:ffffc900010dfde0 EFLAGS: 00010282
Mar 20 21:43:34 agro kernel: RAX: 0000000000000026 RBX:
0000000000000e81 RCX: 0000000000000007
Mar 20 21:43:34 agro kernel: RDX: 0000000000000007 RSI:
0000000000000092 RDI: ffff88881fc587c0
Mar 20 21:43:34 agro kernel: RBP: ffff8887eeb40470 R08:
00000000000004d9 R09: 0000000000000001
Mar 20 21:43:34 agro kernel: R10: 0000000000000000 R11:
0000000000000001 R12: ffff8884f1e28510
Mar 20 21:43:34 agro kernel: R13: ffff88837dc49f30 R14:
0000000000000001 R15: ffff888780b8a840
Mar 20 21:43:34 agro kernel: FS:  0000000000000000(0000)
GS:ffff88881fc40000(0000) knlGS:0000000000000000
Mar 20 21:43:34 agro kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar 20 21:43:34 agro kernel: CR2: 000000000421efb0 CR3:
0000000510564000 CR4: 00000000000006e0
Mar 20 21:43:34 agro kernel: Call Trace:
Mar 20 21:43:34 agro kernel:  nfsd41_destroy_cb+0x36/0x50 [nfsd]
Mar 20 21:43:34 agro kernel:  rpc_free_task+0x3c/0x70 [sunrpc]
Mar 20 21:43:34 agro kernel:  __rpc_execute+0x3a5/0x3c0 [sunrpc]
Mar 20 21:43:34 agro kernel:  ? finish_task_switch+0x7f/0x250
Mar 20 21:43:34 agro kernel:  rpc_async_schedule+0x2f/0x50 [sunrpc]
Mar 20 21:43:34 agro kernel:  process_one_work+0x1ca/0x3c0
Mar 20 21:43:34 agro kernel:  worker_thread+0x45/0x3d0
Mar 20 21:43:34 agro kernel:  kthread+0xf3/0x130
Mar 20 21:43:34 agro kernel:  ? process_one_work+0x3c0/0x3c0
Mar 20 21:43:34 agro kernel:  ? kthread_park+0x80/0x80
Mar 20 21:43:34 agro kernel:  ret_from_fork+0x1f/0x30
Mar 20 21:43:34 agro kernel: ---[ end trace 99765c8e28c46274 ]---