XPost: linux.debian.bugs.dist, linux.kernel   
   From: trondmy@kernel.org   
      
   On Sun, 2025-11-16 at 11:29 -0500, Chuck Lever wrote:   
   > On 11/15/25 7:38 PM, Tyler W. Ross wrote:   
   > > On Friday, November 14th, 2025 at 7:19 AM, Chuck Lever   
   > >  wrote:   
   > > > Then I would say further hunting for the broken commit is going   
   > > > to be   
   > > > fruitless. Adding the WARNs in net/sunrpc/xdr.c is a good next   
   > > > step so   
   > > > we see which XDR data item (assuming it's the same one every   
   > > > time) is   
   > > > failing to decode.   
   > >    
   > > I added WARNs after each trace_rpc_xdr_overflow() call, and then a   
   > > couple   
   > > pr_info() inside xdr_copy_to_scratch() as a follow-up.   
   > >    
   > > If I'm understanding correctly, it's failing in the   
   > > xdr_copy_to_scratch()   
   > > call inside xdr_inline_decode(), because the xdr_stream struct has   
   > > an   
   > > unset/NULL scratch kvec. I don't understand the context enough to   
   > > speculate on why, though.   
   > >    
   > > [   26.844102] Entered xdr_copy_to_scratch()   
   > > [   26.844105] xdr->scratch.iov_base: 0000000000000000   
   > > [   26.844107] xdr->scratch.iov_len: 0   
   > > [   26.844127] ------------[ cut here ]------------   
   > > [   26.844128] WARNING: CPU: 1 PID: 886 at net/sunrpc/xdr.c:1490   
   > > xdr_inline_decode.cold+0x65/0x141 [sunrpc]   
   > > [   26.844153] Modules linked in: rpcsec_gss_krb5 nfsv4   
   > > dns_resolver nfs lockd grace netfs binfmt_misc intel_rapl_msr   
   > > intel_rapl_common kvm_amd ccp kvm cfg80211 hid_generic usbhid hid   
   > > irqbypass rfkill ghash_clmulni_intel aesni_intel pcspkr 8021q garp   
   > > stp virtio_balloon llc mrp button evdev joydev sg auth_rpcgss   
   > > sunrpc configfs efi_pstore nfnetlink vsock_loopback   
   > > vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock   
   > > vmw_vmci qemu_fw_cfg ip_tables x_tables autofs4 ext4 crc16 mbcache   
   > > jbd2 crc32c_cryptoapi sr_mod cdrom bochs uhci_hcd drm_client_lib   
   > > drm_shmem_helper ehci_pci ata_generic sd_mod drm_kms_helper   
   > > ehci_hcd ata_piix libata drm virtio_net usbcore virtio_scsi floppy   
   > > psmouse net_failover failover scsi_mod serio_raw i2c_piix4   
   > > usb_common scsi_common i2c_smbus   
   > > [   26.844217] CPU: 1 UID: 591200003 PID: 886 Comm: ls Not tainted   
   > > 6.17.8-debbug1120598hack3 #9 PREEMPT(lazy)     
   > > [   26.844220] Hardware name: QEMU Standard PC (i440FX + PIIX,   
   > > 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014   
   > > [   26.844222] RIP: 0010:xdr_inline_decode.cold+0x65/0x141 [sunrpc]   
   > > [   26.844238] Code: 24 48 c7 c7 e7 eb 8c c0 48 8b 71 28 e8 5a 36   
   > > fc d7 48 8b 0c 24 4c 8b 44 24 10 48 8b 54 24 08 4c 39 41 28 73 0c   
   > > 0f 1f 44 00 00 <0f> 0b e9 b7 fe fe ff 48 89 d8 48 89 cf 4c 89 44 24   
   > > 08 48 29 d0 48   
   > > [   26.844240] RSP: 0018:ffffd09e82ce3758 EFLAGS: 00010293   
   > > [   26.844242] RAX: 0000000000000017 RBX: ffff8f1e0adcffe8 RCX:   
   > > ffffd09e82ce3838   
   > > [   26.844244] RDX: ffff8f1e0adcffe4 RSI: 0000000000000001 RDI:   
   > > ffff8f1f37c5ce40   
   > > [   26.844245] RBP: ffffd09e82ce37b4 R08: 0000000000000008 R09:   
   > > ffffd09e82ce3600   
   > > [   26.844246] R10: ffffffff9acdb348 R11: 00000000ffffefff R12:   
   > > 000000000000001a   
   > > [   26.844247] R13: ffff8f1e01151200 R14: 0000000000000000 R15:   
   > > 0000000000440000   
   > > [   26.844250] FS:  00007fa5d13db240(0000)   
   > > GS:ffff8f1f9c44a000(0000) knlGS:0000000000000000   
   > > [   26.844252] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033   
   > > [   26.844253] CR2: 00007fa5d13b9000 CR3: 000000010ab82000 CR4:   
   > > 0000000000750ef0   
   > > [   26.844255] PKRU: 55555554   
   > > [   26.844257] Call Trace:   
   > > [   26.844259]     
   > > [   26.844263]  __decode_op_hdr+0x20/0x120 [nfsv4]   
   > > [   26.844288]  nfs4_xdr_dec_readdir+0xbb/0x120 [nfsv4]   
   > > [   26.844305]  gss_unwrap_resp+0x9e/0x150 [auth_rpcgss]   
   > > [   26.844311]  call_decode+0x211/0x230 [sunrpc]   
   > > [   26.844332]  ? __pfx_call_decode+0x10/0x10 [sunrpc]   
   > > [   26.844348]  __rpc_execute+0xb6/0x480 [sunrpc]   
   > > [   26.844369]  ? rpc_new_task+0x17a/0x200 [sunrpc]   
   > > [   26.844386]  rpc_execute+0x133/0x160 [sunrpc]   
   > > [   26.844401]  rpc_run_task+0x103/0x160 [sunrpc]   
   > > [   26.844419]  nfs4_call_sync_sequence+0x74/0xb0 [nfsv4]   
   > > [   26.844440]  _nfs4_proc_readdir+0x28d/0x310 [nfsv4]   
   > > [   26.844459]  nfs4_proc_readdir+0x60/0xf0 [nfsv4]   
   > > [   26.844475]  nfs_readdir_xdr_to_array+0x1fb/0x410 [nfs]   
   > > [   26.844494]  nfs_readdir+0x2ed/0xf00 [nfs]   
   > > [   26.844506]  iterate_dir+0xaa/0x270   
   >    
   > Hi Trond, Anna -   
   >    
      
   [continued in next message]   
      
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