net: bpf: be friendly to kmemcheck

Reported by Mikulas Patocka, kmemcheck currently barks out a
false positive since we don't have special kmemcheck annotation
for bitfields used in bpf_prog structure.

We currently have jited:1, len:31 and thus when accessing len
while CONFIG_KMEMCHECK enabled, kmemcheck throws a warning that
we're reading uninitialized memory.

As we don't need the whole bit universe for pages member, we
can just split it to u16 and use a bool flag for jited instead
of a bitfield.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/arm/net/bpf_jit_32.c

@@ -933,7 +933,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 
 	set_memory_ro((unsigned long)header, header->pages);
 	fp->bpf_func = (void *)ctx.target;
-	fp->jited = 1;
+	fp->jited = true;
 out:
 	kfree(ctx.offsets);
 	return;

arch/mips/net/bpf_jit.c

@@ -1417,7 +1417,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 		bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
 
 	fp->bpf_func = (void *)ctx.target;
-	fp->jited = 1;
+	fp->jited = true;
 
 out:
 	kfree(ctx.offsets);

arch/powerpc/net/bpf_jit_comp.c

@@ -686,7 +686,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 		((u64 *)image)[0] = (u64)code_base;
 		((u64 *)image)[1] = local_paca->kernel_toc;
 		fp->bpf_func = (void *)image;
-		fp->jited = 1;
+		fp->jited = true;
 	}
 out:
 	kfree(addrs);

arch/s390/net/bpf_jit_comp.c

@@ -842,7 +842,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 	if (jit.start) {
 		set_memory_ro((unsigned long)header, header->pages);
 		fp->bpf_func = (void *) jit.start;
-		fp->jited = 1;
+		fp->jited = true;
 	}
 out:
 	kfree(addrs);

arch/sparc/net/bpf_jit_comp.c

@@ -801,7 +801,7 @@ cond_branch:			f_offset = addrs[i + filter[i].jf];
 	if (image) {
 		bpf_flush_icache(image, image + proglen);
 		fp->bpf_func = (void *)image;
-		fp->jited = 1;
+		fp->jited = true;
 	}
 out:
 	kfree(addrs);

arch/x86/net/bpf_jit_comp.c

@@ -955,7 +955,7 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 		bpf_flush_icache(header, image + proglen);
 		set_memory_ro((unsigned long)header, header->pages);
 		prog->bpf_func = (void *)image;
-		prog->jited = 1;
+		prog->jited = true;
 	}
 out:
 	kfree(addrs);

include/linux/filter.h

@@ -300,9 +300,9 @@ struct bpf_work_struct {
 };
 
 struct bpf_prog {
-	u32			pages;		/* Number of allocated pages */
+	u16			pages;		/* Number of allocated pages */
-	u32			jited:1,	/* Is our filter JIT'ed? */
+	bool			jited;		/* Is our filter JIT'ed? */
-				len:31;		/* Number of filter blocks */
+	u32			len;		/* Number of filter blocks */
 	struct sock_fprog_kern	*orig_prog;	/* Original BPF program */
 	struct bpf_work_struct	*work;		/* Deferred free work struct */
 	unsigned int		(*bpf_func)(const struct sk_buff *skb,

net/core/filter.c

@@ -972,7 +972,7 @@ static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp)
 	int err;
 
 	fp->bpf_func = NULL;
-	fp->jited = 0;
+	fp->jited = false;
 
 	err = bpf_check_classic(fp->insns, fp->len);
 	if (err) {