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SubjectWARNING in bpf_check (3)

syzbot found the following crash on:

HEAD commit: 13fac1d8 bpf: Fix trampoline generation for fmod_ret progr..
git tree: bpf-next
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:
C reproducer:

The bug was bisected to:

commit 94dacdbd5d2dfa2cffd308f128d78c99f855f5be
Author: Thomas Gleixner <>
Date: Mon Feb 24 14:01:32 2020 +0000

bpf: Tighten the requirements for preallocated hash maps

bisection log:
final crash:
console output:

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Fixes: 94dacdbd5d2d ("bpf: Tighten the requirements for preallocated hash maps")

------------[ cut here ]------------
trace type BPF program uses run-time allocation
WARNING: CPU: 1 PID: 9523 at kernel/bpf/verifier.c:8187 check_map_prog_compatibility kernel/bpf/verifier.c:8187 [inline]
WARNING: CPU: 1 PID: 9523 at kernel/bpf/verifier.c:8187 replace_map_fd_with_map_ptr kernel/bpf/verifier.c:8282 [inline]
WARNING: CPU: 1 PID: 9523 at kernel/bpf/verifier.c:8187 bpf_check+0x6dcb/0xa49b kernel/bpf/verifier.c:10112
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 9523 Comm: syz-executor700 Not tainted 5.6.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x35 kernel/panic.c:582
report_bug+0x27b/0x2f0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:check_map_prog_compatibility kernel/bpf/verifier.c:8187 [inline]
RIP: 0010:replace_map_fd_with_map_ptr kernel/bpf/verifier.c:8282 [inline]
RIP: 0010:bpf_check+0x6dcb/0xa49b kernel/bpf/verifier.c:10112
Code: ff 48 8b bd 20 fe ff ff e8 02 56 2c 00 e9 bc cf ff ff e8 88 a0 ef ff 48 c7 c7 c0 8c 11 88 c6 05 c0 c7 de 08 01 e8 bd b3 c1 ff <0f> 0b e9 f3 ae ff ff c7 85 c0 fe ff ff f4 ff ff ff e9 d3 c6 ff ff
RSP: 0018:ffffc90001ec7990 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815bfd81 RDI: fffff520003d8f24
RBP: ffffc90001ec7b90 R08: ffff88809ae22380 R09: ffffed1015ce45c9
R10: ffffed1015ce45c8 R11: ffff8880ae722e43 R12: 0000000000000002
R13: ffffc90000d36048 R14: ffff88809a7d4800 R15: dffffc0000000000
bpf_prog_load+0xd92/0x15f0 kernel/bpf/syscall.c:2105
__do_sys_bpf+0x16f2/0x4020 kernel/bpf/syscall.c:3594
do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:294
RIP: 0033:0x440539
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdd65517e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440539
RDX: 0000000000000014 RSI: 0000000020fed000 RDI: 0000000000000005
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401dc0
R13: 0000000000401e50 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..

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