Re: [PATCH v2 4/4] powerpc/bpf: use bpf_jit_binary_pack_[alloc|finalize|free]

[Hari Bathini <hbathini@linux.ibm.com>]

On 11/03/23 3:46 pm, Christophe Leroy wrote:
> 
> 
> Le 09/03/2023 à 19:02, Hari Bathini a écrit :
>> Use bpf_jit_binary_pack_alloc in powerpc jit. The jit engine first
>> writes the program to the rw buffer. When the jit is done, the program
>> is copied to the final location with bpf_jit_binary_pack_finalize.
>> With multiple jit_subprogs, bpf_jit_free is called on some subprograms
>> that haven't got bpf_jit_binary_pack_finalize() yet. Implement custom
>> bpf_jit_free() like in commit 1d5f82d9dd47 ("bpf, x86: fix freeing of
>> not-finalized bpf_prog_pack") to call bpf_jit_binary_pack_finalize(),
>> if necessary. While here, correct the misnomer powerpc64_jit_data to
>> powerpc_jit_data as it is meant for both ppc32 and ppc64.
> 
> root@vgoip:~# echo 1 > /proc/sys/net/core/bpf_jit_enable
> root@vgoip:~# insmod test_bpf.ko
> [  570.270983] kernel tried to execute exec-protected page (bd42c198) -
> exploit attempt? (uid: 0)
> [  570.279414] BUG: Unable to handle kernel instruction fetch
> [  570.284822] Faulting instruction address: 0xbd42c198
> [  570.289734] Oops: Kernel access of bad area, sig: 11 [#1]
> [  570.295062] BE PAGE_SIZE=16K PREEMPT CMPC885
> [  570.302811] Modules linked in: test_bpf(+) test_module
> [  570.307891] CPU: 0 PID: 559 Comm: insmod Not tainted
> 6.3.0-rc1-s3k-dev-g4ae0418b3500 #258
> [  570.315975] Hardware name: MIAE 8xx 0x500000 CMPC885
> [  570.320882] NIP:  bd42c198 LR: be8180ec CTR: be818010
> [  570.325873] REGS: cae2bc40 TRAP: 0400   Not tainted
> (6.3.0-rc1-s3k-dev-g4ae0418b3500)
> [  570.333704] MSR:  40009032 <EE,ME,IR,DR,RI>  CR: 88008222  XER: 00000000
> [  570.340503]
> [  570.340503] GPR00: be806eac cae2bd00 c2977340 00000000 c2c40900
> 00000000 c1a18a80 00000000
> [  570.340503] GPR08: 00000002 00000001 00000000 00000000 ffffffff
> 100d815e ca6a0000 00000001
> [  570.340503] GPR16: 1234aaaa ca242250 c1180000 00000001 1234aaab
> c9050030 00000000 00000000
> [  570.340503] GPR24: c2c40900 00000000 ffffffff 00000000 c1a18a80
> 00000000 00000002 ca24225c
> [  570.376819] NIP [bd42c198] 0xbd42c198
> [  570.380436] LR [be8180ec] 0xbe8180ec
> [  570.383965] Call Trace:
> [  570.386373] [cae2bd00] [0000000b] 0xb (unreliable)
> [  570.391107] [cae2bd50] [be806eac] __run_one+0x58/0x224 [test_bpf]
> [  570.397390] [cae2bd90] [be80ca94] test_bpf_init+0x8d8/0x1010 [test_bpf]
> [  570.404189] [cae2be20] [c00049f0] do_one_initcall+0x38/0x1e4
> [  570.409782] [cae2be80] [c0090aa8] do_init_module+0x50/0x234
> [  570.415291] [cae2bea0] [c0092e08] sys_finit_module+0xb4/0xf8
> [  570.420884] [cae2bf20] [c000e344] system_call_exception+0x94/0x150
> [  570.426995] [cae2bf30] [c00120a8] ret_from_syscall+0x0/0x28
> [  570.432502] --- interrupt: c00 at 0xfd5fca0
> [  570.436632] NIP:  0fd5fca0 LR: 10014568 CTR: 10013294
> [  570.441625] REGS: cae2bf40 TRAP: 0c00   Not tainted
> (6.3.0-rc1-s3k-dev-g4ae0418b3500)
> [  570.449455] MSR:  0000d032 <EE,PR,ME,IR,DR,RI>  CR: 44002224  XER:
> 00000000
> [  570.456513]
> [  570.456513] GPR00: 00000161 7f868d30 77ed34d0 00000003 100bc4ef
> 00000000 0fd51868 0000d032
> [  570.456513] GPR08: 000007b1 10013294 00000000 00000002 52454753
> 100d815e 100a44b8 00000000
> [  570.456513] GPR16: 100d167c 100b0000 1198426c 119854cd 100d0000
> 100d0000 00000000 100a4498
> [  570.456513] GPR24: ffffffa2 ffffffff 11984244 00000003 1198426c
> 100bc4ef 11984288 1198426c
> [  570.492828] NIP [0fd5fca0] 0xfd5fca0
> [  570.496358] LR [10014568] 0x10014568
> [  570.499887] --- interrupt: c00
> [  570.502902] Code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
> XXXXXXXX XXXXXXXX XXXXXXXX
> [  570.517973] ---[ end trace 0000000000000000 ]---
> [  570.522523]
> [  570.523986] note: insmod[559] exited with irqs disabled
> Segmentation fault

Thanks a lot for reviewing v2, Christophe.
Posted v3 for reviewing..

Thanks
Hari