This is an informative email report,

On linux-next while running kselftest bpf test_verifier, the following kernel warning reported. But this seems to be NOT a kernel regression after reading the commit log.

Started noticing from 5.6.0-rc3-next-20200226 and still happening on 5.6.0-rc4-next-20200306.

Suspecting patch, commit id 94dacdbd5d2dfa2cffd308f128d78c99f855f5be " bpf: Tighten the requirements for preallocated hash maps <> So preallocation _must_ be enforced for all variants of intrusive instrumentation.

Unfortunately immediate enforcement would break backwards compatibility, so for now such programs still are allowed to run, but a one time warning is emitted in dmesg and the verifier emits a warning in the verifier log as well so developers are made aware about this and can fix their programs before the enforcement becomes mandatory.

Link: https://lore.kernel.org/bpf/20200224145642.540542802@linutronix.de " steps to reproduce: steps: - cd /opt/kselftests/default-in-kernel/bpf - ./test_verifier || true

[ 0.000000] Linux version 5.6.0-rc3-next-20200226 (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP Wed Feb 26 04:46:18 UTC 2020 <Trim> [ 54.263845] trace type BPF program uses run-time allocation [ 54.269438] WARNING: CPU: 1 PID: 473 at /usr/src/kernel/kernel/bpf/verifier.c:8186 bpf_check+0x2332/0x30a4 [ 54.280445] Modules linked in: x86_pkg_temp_thermal fuse [ 54.285759] CPU: 1 PID: 473 Comm: test_verifier Not tainted 5.6.0-rc3-next-20200226 #1 [ 54.293669] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 54.301054] RIP: 0010:bpf_check+0x2332/0x30a4 [ 54.305412] Code: ff ff 48 c7 c7 b8 91 5e a8 4c 89 85 10 ff ff ff 48 89 95 18 ff ff ff 48 89 85 20 ff ff ff c6 05 e1 54 98 01 01 e8 4e 16 ea ff <0f> 0b 4c 8b 85 10 ff ff ff 48 8b 95 18 ff ff ff 48 8b 85 20 ff ff [ 54.324149] RSP: 0018:ffffbf708061bc48 EFLAGS: 00010282 [ 54.329365] RAX: 0000000000000000 RBX: ffffa0a66b5ad200 RCX: 0000000000000000 [ 54.336489] RDX: 0000000000000001 RSI: ffffa0a66fa98d48 RDI: ffffa0a66fa98d48 [ 54.343614] RBP: ffffbf708061bd48 R08: 0000000000000000 R09: 0000000000000000 [ 54.350736] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0a667a90000 [ 54.357863] R13: 0000000000000004 R14: 0000000000000000 R15: ffffbf7080069058 [ 54.364993] FS: 00007fd8b7cd4740(0000) GS:ffffa0a66fa80000(0000) knlGS:0000000000000000 [ 54.373070] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 54.378807] CR2: 000000000098e65c CR3: 0000000231bf6001 CR4: 00000000003606e0 [ 54.385931] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 54.393054] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 54.400180] Call Trace: [ 54.402633] ? lockdep_hardirqs_on+0xf6/0x190 [ 54.406993] ? ktime_get_with_offset+0x7a/0x130 [ 54.411525] ? trace_hardirqs_on+0x4c/0x100 [ 54.415714] bpf_prog_load+0x57d/0x6f0 [ 54.419466] ? __might_fault+0x3e/0x90 [ 54.423221] ? selinux_bpf+0x5a/0x80 [ 54.426806] __do_sys_bpf+0xd69/0x1cd0 [ 54.430565] __x64_sys_bpf+0x1a/0x20 [ 54.434146] do_syscall_64+0x55/0x200 [ 54.437812] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 54.442862] RIP: 0033:0x7fd8b6d9af59 [ 54.446441] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 8b 0d 0f ff 2b 00 f7 d8 64 89 01 48 [ 54.465179] RSP: 002b:00007ffd5bac5238 EFLAGS: 00000202 ORIG_RAX: 0000000000000141 [ 54.472743] RAX: ffffffffffffffda RBX: 00007ffd5bac53ec RCX: 00007fd8b6d9af59 [ 54.479867] RDX: 0000000000000078 RSI: 00007ffd5bac52b0 RDI: 0000000000000005 [ 54.486991] RBP: 00007ffd5bac5250 R08: 00007ffd5bac53f8 R09: 00007ffd5bac52b0 [ 54.494115] R10: 000000000098e638 R11: 0000000000000202 R12: 0000000000000005 [ 54.501239] R13: 000000000098e630 R14: 0000000000000001 R15: 0000000000000000 [ 54.508368] irq event stamp: 82014 [ 54.511770] hardirqs last enabled at (82013): [<ffffffffa6f775ed>] console_unlock+0x45d/0x5c0 [ 54.520374] hardirqs last disabled at (82014): [<ffffffffa6e01f3b>] trace_hardirqs_off_thunk+0x1a/0x1c [ 54.529666] softirqs last enabled at (82000): [<ffffffffa8000338>] __do_softirq+0x338/0x43a [ 54.538096] softirqs last disabled at (81963): [<ffffffffa6f04588>] irq_exit+0xb8/0xc0 [ 54.545999] ---[ end trace 75d82c4cbb8fc047 ]---

metadata: git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git git branch: master git describe: next-20200226 make_kernelversion: 5.6.0-rc3 kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/intel-corei7-64/lkft...

Full test log, https://lkft.validation.linaro.org/scheduler/job/1251016#L1416 https://lkft.validation.linaro.org/scheduler/job/1269522#L1509 https://lkft.validation.linaro.org/scheduler/job/1269575#L1501