bionic: prevent root processes from calling __system_property_add
If a root process other than init calls __system_property_add, which
it should never do, it will break the design assumption that there is
only one mutator.
Pass O_EXCL to open() in map_prop_region_rw to ensure that only one
process ever has the property pages open for write.
Change-Id: I6b7c118e5e2fd2b92a2b168b8454fe9707325462
diff --git a/libc/bionic/system_properties.c b/libc/bionic/system_properties.c
index d4054d2..f9671c6 100644
--- a/libc/bionic/system_properties.c
+++ b/libc/bionic/system_properties.c
@@ -128,11 +128,13 @@
{
prop_area *pa;
int fd;
+ int ret;
/* dev is a tmpfs that we can use to carve a shared workspace
* out of, so let's do that...
*/
- fd = open(property_filename, O_RDWR | O_CREAT | O_NOFOLLOW, 0644);
+ fd = open(property_filename, O_RDWR | O_CREAT | O_NOFOLLOW | O_CLOEXEC |
+ O_EXCL, 0444);
if (fd < 0) {
if (errno == EACCES) {
/* for consistency with the case where the process has already
@@ -143,6 +145,10 @@
return -1;
}
+ ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
+ if (ret < 0)
+ goto out;
+
if (ftruncate(fd, PA_SIZE) < 0)
goto out;
@@ -186,8 +192,16 @@
{
bool fromFile = true;
int result = -1;
+ int fd;
+ int ret;
- int fd = open(property_filename, O_RDONLY | O_NOFOLLOW);
+ fd = open(property_filename, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
+ if (fd >= 0) {
+ /* For old kernels that don't support O_CLOEXEC */
+ ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
+ if (ret < 0)
+ goto cleanup;
+ }
if ((fd < 0) && (errno == ENOENT)) {
/*