/proc/iomem: only expose physical resource addresses to privileged users

[Mark Salyzyn <salyzyn@android.com>]

From: Linus Torvalds <torvalds@linux-foundation.org>

commit 51d7b120418e99d6b3bf8df9eb3cc31e8171dee4 upstream ported to
3.18.y

In commit c4004b02f8e5b ("x86: remove the kernel code/data/bss resources
from /proc/iomem") I was hoping to remove the phyiscal kernel address
data from /proc/iomem entirely, but that had to be reverted because some
system programs actually use it.

This limits all the detailed resource information to properly
credentialed users instead.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org # 3.18
---
 kernel/resource.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index d9c7d5d77c8a..83658ca0e69c 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -104,16 +104,25 @@ static int r_show(struct seq_file *m, void *v)
 {
 	struct resource *root = m->private;
 	struct resource *r = v, *p;
+	unsigned long long start, end;
 	int width = root->end < 0x10000 ? 4 : 8;
 	int depth;
 
 	for (depth = 0, p = r; depth < MAX_IORES_LEVEL; depth++, p = p->parent)
 		if (p->parent == root)
 			break;
+
+	if (file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN)) {
+		start = r->start;
+		end = r->end;
+	} else {
+		start = end = 0;
+	}
+
 	seq_printf(m, "%*s%0*llx-%0*llx : %s\n",
 			depth * 2, "",
-			width, (unsigned long long) r->start,
-			width, (unsigned long long) r->end,
+			width, start,
+			width, end,
 			r->name ? r->name : "<BAD>");
 	return 0;
 }
-- 
2.19.1.930.g4563a0d9d0-goog