Linux kernel module programming guide. Module (for procfs) behaves differently with cat and python3

Question

I read sections 7.0-7.1 about procfs from Linux kernel module programming guide and tried to run example procfs1.c. It's work, but I have some questions.

1. Why we don't use try_module_get and module_put in procfs module, but use in chardev module? There is this text, but I don't understand why we don’t get called when the file is opened or closed.

Because we don’t get called when the file is opened or closed, there’s nowhere for us to put try_module_get and module_put in this module, and if the file is opened and then the module is removed, there’s no way to avoid the consequences.

2. I compiled procfs1.c and load module successfully.

msedlyarskiy@my-dev ~/l/procfs1> sudo insmod procfs1.ko
msedlyarskiy@my-dev ~/l/procfs1> sudo cat /proc/helloworld
HelloWorld!

Then, I executed cat and got this dmesg output:

[1326668.263173] procfs1: loading out-of-tree module taints kernel.
[1326668.263316] procfs1: module verification failed: signature and/or required key missing - tainting kernel
[1326668.263633] /proc/helloworld created
[1326686.364398] procfile read helloworld
[1326686.364412] copy_to_user failed

All right. But then I tried to open mounted proc file by python3.

msedlyarskiy@my-dev ~/l/procfs1> sudo python3
Python 3.10.12 (main, Jun 11 2023, 05:26:28) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> f = open('/proc/helloworld', "r", encoding="utf-8")
fish: Job 1, 'python3' terminated by signal SIGKILL (Forced quit)

Python3 failed and in dmesg I found some errors:

[1327018.190609] R13: 00005648566695a0 R14: 0000000000000001 R15: 0000000000000003
[1327018.191691]  </TASK>
[1327018.192044] Modules linked in: procfs1(OE) cpuid tls xt_conntrack nft_chain_nat xt_MASQUERADE nf_nat nf_conntrack_netlink nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 xfrm_user xfrm_algo nft_counter xt_addrtype nft_compat nf_tables nfnetlink br_netfilter bridge stp llc overlay intel_rapl_msr intel_rapl_common joydev nfit input_leds mac_hid serio_raw qemu_fw_cfg binfmt_misc sch_fq_codel dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua ipmi_devintf ipmi_msghandler msr pstore_blk ramoops pstore_zone reed_solomon efi_pstore ip_tables x_tables autofs4 btrfs blake2b_generic zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic usbhid hid bochs drm_vram_helper drm_ttm_helper ttm drm_kms_helper crct10dif_pclmul syscopyarea sysfillrect sysimgblt crc32_pclmul fb_sys_fops ghash_clmulni_intel cec aesni_intel rc_core virtio_net net_failover crypto_simd i2c_i801 psmouse failover cryptd drm virtio_blk
[1327018.192107]  lpc_ich i2c_smbus
[1327018.204675] CR2: 0000000000000000
[1327018.205180] ---[ end trace 198b4be9390f4bd4 ]---
[1327018.205891] RIP: 0010:0x0
[1327018.206299] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[1327018.212234] RSP: 0018:ff4bcacdc0e9be20 EFLAGS: 00010246
[1327018.212997] RAX: 0000000000000000 RBX: ff4148699643f780 RCX: 0000000000000001
[1327018.214029] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ff4148699566d200
[1327018.215090] RBP: ff4bcacdc0e9be38 R08: 0000000000000003 R09: 0000000000000000
[1327018.216153] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
[1327018.217192] R13: 0000000000000000 R14: ffffffffffffffea R15: ff4148699566d200
[1327018.218200] FS:  00007f432a0531c0(0000) GS:ff41486bf3cc0000(0000) knlGS:0000000000000000
[1327018.219299] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[1327018.220111] CR2: ffffffffffffffd6 CR3: 000000010e5b0002 CR4: 0000000000771ee0
[1327018.221107] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[1327018.222086] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[1327018.223073] PKRU: 55555554

It's similar to trying executed nonexistent code, but I am not sure. I couldn't unload module because rmmod stucked.

Can you help me to understand why can cat read proc file but python3 can't?