powerpc/bpf: Fix write protecting JIT code
authorHari Bathini <hbathini@linux.ibm.com>
Mon, 25 Oct 2021 05:56:49 +0000 (11:26 +0530)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 27 Oct 2021 13:08:32 +0000 (00:08 +1100)
commit44a8214de96bafb5210e43bfa2c97c19bf75af3d
treecdfb0d8098d65f703b1ebfbbe06e7c4c446d1604
parentcb662608e546d755e3e1b51b30a269459323bf24
powerpc/bpf: Fix write protecting JIT code

Running program with bpf-to-bpf function calls results in data access
exception (0x300) with the below call trace:

  bpf_int_jit_compile+0x238/0x750 (unreliable)
  bpf_check+0x2008/0x2710
  bpf_prog_load+0xb00/0x13a0
  __sys_bpf+0x6f4/0x27c0
  sys_bpf+0x2c/0x40
  system_call_exception+0x164/0x330
  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.

Fixes: 62e3d4210ac9 ("powerpc/bpf: Write protect JIT code")
Cc: stable@vger.kernel.org # v5.14+
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211025055649.114728-1-hbathini@linux.ibm.com
arch/powerpc/net/bpf_jit_comp.c