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

[Hari Bathini]

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(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index fcbf7a917c56..90ce75f0f1e2 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -241,8 +241,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 	fp->jited_len = alloclen;
 
 	bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
-	bpf_jit_binary_lock_ro(bpf_hdr);
 	if (!fp->is_func || extra_pass) {
+		bpf_jit_binary_lock_ro(bpf_hdr);
 		bpf_prog_fill_jited_linfo(fp, addrs);
 out_addrs:
 		kfree(addrs);
-- 
2.31.1