Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call

Peter Zijlstra
2023-12-04T18:16:37Z

On Mon, Dec 04, 2023 at 06:25:34PM +0100, Jiri Olsa wrote:

> that boots properly for me but gives crash below when running bpf tests

OK, more funnies..

> [ 482.145182][ T699] RIP: 0010:bpf_for_each_array_elem+0xbb/0x120
> [ 482.145672][ T699] Code: 4c 01 f5 89 5c 24 04 4c 89 e7 48 8d 74 24 04 48 89 ea 4c 89 fd 4c 89 f9 45 31 c0 4d 89 eb 41 ba ef 86 cd 67 45 03 53 f1 74 02 <0f> 0b 41 ff d3 0f 1f 00 48 85 c0 75 0e 48 8d 43 01 41 8b 4c 24 24
> [ 482.147221][ T699] RSP: 0018:ffffc900017e3e88 EFLAGS: 00010217
> [ 482.147702][ T699] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc900017e3ed8
> [ 482.152162][ T699] RDX: ffff888152eb0210 RSI: ffffc900017e3e8c RDI: ffff888152eb0000
> [ 482.152770][ T699] RBP: ffffc900017e3ed8 R08: 0000000000000000 R09: 0000000000000000
> [ 482.153350][ T699] R10: 000000004704ef28 R11: ffffffffa0012774 R12: ffff888152eb0000
> [ 482.153951][ T699] R13: ffffffffa0012774 R14: ffff888152eb0210 R15: ffffc900017e3ed8
> [ 482.154554][ T699] FS: 00007fa60d4fdd00(0000) GS:ffff88846d200000(0000) knlGS:0000000000000000
> [ 482.155138][ T699] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 482.155564][ T699] CR2: 00007fa60d7d8000 CR3: 00000001502a2005 CR4: 0000000000770ef0
> [ 482.156095][ T699] PKRU: 55555554
> [ 482.156349][ T699] Call Trace:
> [ 482.156596][ T699] <TASK>
> [ 482.156816][ T699] ? __die_body+0x68/0xb0
> [ 482.157138][ T699] ? die+0xba/0xe0
> [ 482.157456][ T699] ? do_trap+0xa5/0x180
> [ 482.157826][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> [ 482.158277][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> [ 482.158711][ T699] ? do_error_trap+0xc4/0x140
> [ 482.159052][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> [ 482.159506][ T699] ? handle_invalid_op+0x2c/0x40
> [ 482.159906][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> [ 482.160990][ T699] ? exc_invalid_op+0x38/0x60
> [ 482.161375][ T699] ? asm_exc_invalid_op+0x1a/0x20
> [ 482.161788][ T699] ? 0xffffffffa0012774
> [ 482.162149][ T699] ? 0xffffffffa0012774
> [ 482.162513][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> [ 482.162905][ T699] bpf_prog_ca45ea7f9cb8ac1a_inner_map+0x94/0x98
> [ 482.163471][ T699] bpf_trampoline_6442549234+0x47/0x1000

Looks like this trips an #UD, I'll go try and figure out what this
bpf_for_each_array_elem() does to cause this. Looks like it has an
indirect call, could be the callback_fn thing has a CFI mis-match.