[PATCH] powerpc/bpf: fix write protecting JIT code

[Naveen N. Rao]

Hari Bathini wrote:
> Running program with bpf-to-bpf function calls results in data access
> exception (0x300) with the below call trace:
> 
>     [c000000000113f28] bpf_int_jit_compile+0x238/0x750 (unreliable)
>     [c00000000037d2f8] bpf_check+0x2008/0x2710
>     [c000000000360050] bpf_prog_load+0xb00/0x13a0
>     [c000000000361d94] __sys_bpf+0x6f4/0x27c0
>     [c000000000363f0c] sys_bpf+0x2c/0x40
>     [c000000000032434] system_call_exception+0x164/0x330
>     [c00000000000c1e8] system_call_vectored_common+0xe8/0x278
> 
> as bpf_int_jit_compile() tries writing to write protected JIT code
> location during the extra pass.
> 
> Fix it by holding off write protection of JIT code until the extra
> pass, where branch target addresses fixup happens.
> 
> Cc: stable at vger.kernel.org
> Fixes: 62e3d4210ac9 ("powerpc/bpf: Write protect JIT code")
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> ---
>  arch/powerpc/net/bpf_jit_comp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks for the fix!

Reviewed-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>