[PATCH v10 05/10] powerpc/bpf: Write protect JIT code

[Jordan Niethe]

Once CONFIG_STRICT_MODULE_RWX is enabled there will be no need to
override bpf_jit_free() because it is now possible to set images
read-only. So use the default implementation.

Also add the necessary call to bpf_jit_binary_lock_ro() which will
remove write protection and add exec protection to the JIT image after
it has finished being written.

Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
---
v10: New to series
---
 arch/powerpc/net/bpf_jit_comp.c   | 5 ++++-
 arch/powerpc/net/bpf_jit_comp64.c | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index e809cb5a1631..8015e4a7d2d4 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -659,12 +659,15 @@ void bpf_jit_compile(struct bpf_prog *fp)
 		bpf_jit_dump(flen, proglen, pass, code_base);
 
 	bpf_flush_icache(code_base, code_base + (proglen/4));
-
 #ifdef CONFIG_PPC64
 	/* Function descriptor nastiness: Address + TOC */
 	((u64 *)image)[0] = (u64)code_base;
 	((u64 *)image)[1] = local_paca->kernel_toc;
 #endif
+	if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
+		set_memory_ro((unsigned long)image, alloclen >> PAGE_SHIFT);
+		set_memory_x((unsigned long)image, alloclen >> PAGE_SHIFT);
+	}
 
 	fp->bpf_func = (void *)image;
 	fp->jited = 1;
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index aaf1a887f653..1484ad588685 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -1240,6 +1240,8 @@ 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));
+	if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		bpf_jit_binary_lock_ro(bpf_hdr);
 	if (!fp->is_func || extra_pass) {
 		bpf_prog_fill_jited_linfo(fp, addrs);
 out_addrs:
@@ -1262,6 +1264,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 }
 
 /* Overriding bpf_jit_free() as we don't set images read-only. */
+#ifndef CONFIG_STRICT_MODULE_RWX
 void bpf_jit_free(struct bpf_prog *fp)
 {
 	unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
@@ -1272,3 +1275,4 @@ void bpf_jit_free(struct bpf_prog *fp)
 
 	bpf_prog_unlock_free(fp);
 }
+#endif
-- 
2.25.1