linux-5.4.51 cfg80211 fails to load regulatory.db when compiled with gcc-10.1.0 and glibc-2.31

When compiling 5.4.51 natively on an RPi4 using bcm2711_defconfig with gcc-10.1.0 and glibc-2.31, cfg80211 fails to load regulatory.db - there are no errors or relevant warnings during the compilation.

Using a cross-compiler "arm-bcm2708hf-linux-gnueabihf-gcc (crosstool-NG 1.24.0.6-afaf7b9) 7.4.1 20181213" and glibc-2.28 with the same config except "CONFIG_CC_HAS_ASM_INLINE=y" (not supported by gcc-7) results in no problems.

In both cases wifi works.

[    1.215627] Asymmetric key parser 'x509' registered
[    1.491309] Loading compiled-in X.509 certificates
...
[60597.353367] cfg80211: Problem loading in-kernel X.509 certificate (-22)
[60597.365221] ------------[ cut here ]------------
[60597.365240] WARNING: CPU: 2 PID: 12380 at crypto/rsa-pkcs1pad.c:539 pkcs1pad_verify+0x158/0x174
[60597.365248] Modules linked in: cfg80211 rfkill snd_soc_bcm2835_i2s snd_soc_core snd_pcm_dmaengine snd_compress snd_bcm2835(C) snd_pcm snd_timer snd i2c_dev evdev squashfs spidev rpivid_mem raspberrypi_hwmon spi_bcm2835 i2c_bcm2835 zram zsmalloc uio_pdrv_genirq uio
[60597.365313] CPU: 2 PID: 12380 Comm: modprobe Not tainted 5.4.51-piCore-v7 #1
[60597.365317] Hardware name: BCM2711
[60597.365328] Workqueue: events request_firmware_work_func
[60597.365333] Backtrace: 
[60597.365346] [<c020df24>] (dump_backtrace) from [<c020e26c>] (show_stack+0x20/0x24)
[60597.365353]  r7:ffffffff r6:00000000 r5:60000013 r4:c129c7a0
[60597.365363] [<c020e24c>] (show_stack) from [<c0a5e38c>] (dump_stack+0xd0/0x114)
[60597.365372] [<c0a5e2bc>] (dump_stack) from [<c0221e28>] (__warn+0xe0/0x108)
[60597.365380]  r9:cfd14c00 r8:00000009 r7:0000021b r6:c0639948 r5:00000009 r4:c0dedd50
[60597.365389] [<c0221d48>] (__warn) from [<c02221f4>] (warn_slowpath_fmt+0x74/0xcc)
[60597.365395]  r7:c0639948 r6:0000021b r5:c0dedd50 r4:00000000
[60597.365404] [<c0222184>] (warn_slowpath_fmt) from [<c0639948>] (pkcs1pad_verify+0x158/0x174)
[60597.365411]  r8:cfd27300 r7:cfdf4880 r6:cfdacdc0 r5:00000000 r4:cfd27300
[60597.365421] [<c06397f0>] (pkcs1pad_verify) from [<c06432c4>] (public_key_verify_signature+0x258/0x304)
[60597.365428]  r9:cfd14c00 r8:cfd27300 r7:cfdf4880 r6:cfdacdc0 r5:00000000 r4:d1467c0c
[60597.365437] [<c064306c>] (public_key_verify_signature) from [<c06448cc>] (x509_check_for_self_signed+0xcc/0x128)
[60597.365444]  r9:000000ef r8:000002a8 r7:cfdacd80 r6:00000000 r5:cfdacdc0 r4:cfdf4780
[60597.365453] [<c0644800>] (x509_check_for_self_signed) from [<c0643cc0>] (x509_cert_parse+0x178/0x1c8)
[60597.365459]  r7:f082103c r6:cfdf4800 r5:cfdacf00 r4:cfdf4780
[60597.365468] [<c0643b48>] (x509_cert_parse) from [<c0644f94>] (pkcs7_extract_cert+0x3c/0x70)
[60597.365475]  r9:000000ef r8:0000004f r7:00000000 r6:000002a4 r5:00000002 r4:cfdacc80
[60597.365484] [<c0644f58>] (pkcs7_extract_cert) from [<c06a4270>] (asn1_ber_decoder+0x648/0x920)
[60597.365489]  r5:00000002 r4:00000040
[60597.365497] [<c06a3c28>] (asn1_ber_decoder) from [<c0644b18>] (pkcs7_parse_message+0xdc/0x1ac)
[60597.365504]  r10:00000000 r9:cfdacd00 r8:cfdacd00 r7:0000049e r6:f0821000 r5:c0e4040c
[60597.365509]  r4:cfdacc80
[60597.365519] [<c0644a3c>] (pkcs7_parse_message) from [<c037aa04>] (verify_pkcs7_signature+0x2c/0x80)
[60597.365527]  r9:00000080 r8:00000000 r7:eff3e600 r6:00000eb4 r5:f081b000 r4:f081b000
[60597.365641] [<c037a9d8>] (verify_pkcs7_signature) from [<bf1ae104>] (valid_regdb+0xd8/0x228 [cfg80211])
[60597.365647]  r6:bf21f554 r5:00000eb4 r4:f081b000
[60597.365827] [<bf1ae02c>] (valid_regdb [cfg80211]) from [<bf1b20d4>] (regdb_fw_cb+0x34/0x114 [cfg80211])
[60597.365835]  r10:00000000 r9:00000080 r8:00000000 r7:eff3e600 r6:cfdac900 r5:bf21f554
[60597.365840]  r4:cfdac840
[60597.365933] [<bf1b20a0>] (regdb_fw_cb [cfg80211]) from [<c078b628>] (request_firmware_work_func+0x60/0xa4)
[60597.365940]  r7:eff3e600 r6:eff3b340 r5:eee87e00 r4:cfdac8c0
[60597.365951] [<c078b5c8>] (request_firmware_work_func) from [<c023f468>] (process_one_work+0x21c/0x544)
[60597.365956]  r4:cfdac8c0
[60597.365964] [<c023f24c>] (process_one_work) from [<c023f7fc>] (worker_thread+0x6c/0x5d8)
[60597.365972]  r10:eff3b340 r9:00000008 r8:c1203d00 r7:eff3b358 r6:eee87e14 r5:eff3b340
[60597.365976]  r4:eee87e00
[60597.365984] [<c023f790>] (worker_thread) from [<c02460a8>] (kthread+0x16c/0x170)
[60597.365992]  r10:d0f57e84 r9:c023f790 r8:eee87e00 r7:d1466000 r6:00000000 r5:eee86a40
[60597.365996]  r4:efbb6540
[60597.366004] [<c0245f3c>] (kthread) from [<c02010ac>] (ret_from_fork+0x14/0x28)
[60597.366009] Exception stack(0xd1467fb0 to 0xd1467ff8)
[60597.366015] 7fa0:                                     00000000 00000000 00000000 00000000
[60597.366022] 7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[60597.366028] 7fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[60597.366036]  r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c0245f3c
[60597.366040]  r4:eee86a40
[60597.366046] ---[ end trace 8ac9463ac2468c2b ]---
[60597.366072] cfg80211: loaded regulatory.db is malformed or signature is missing/invalid

Start with crypto/rsa-pkcs1pad.c at pkcs1pad_verify, then follow cfg80211's valid_regdb and regdb_fw_cb paths shown in the trace. Reproduce the native GCC 10.1.0/glibc 2.31 build and compare it with the GCC 7.4.1 cross-build; done means regulatory.db loads without the certificate or malformed-signature warning.