init: harden socket creation against symlinks
Instead of using chown, use the symlink safe lchown.
Instead of using chmod, use the symlink safe fchmodat
with AT_SYMLINK_NOFOLLOW.
Fix a bug where the SELinux filesystem creation context may
not be restored, and some memory not freed, if bind() fails.
Check the return values from the chown/chmod calls and unlink
the files if it ever fails.
(cherrypicked from commit ab5629c197ae278992039a9685df047fe34232b8)
Bug: 27337831
Change-Id: I28c5f4dee55aa706437eb51ad403c1fbf56138de
diff --git a/init/util.cpp b/init/util.cpp
index aefdf8f..84b4155 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -102,7 +102,7 @@
gid_t gid, const char *socketcon)
{
struct sockaddr_un addr;
- int fd, ret;
+ int fd, ret, savederrno;
char *filecon;
if (socketcon) {
@@ -140,16 +140,26 @@
}
ret = bind(fd, (struct sockaddr *) &addr, sizeof (addr));
- if (ret) {
- ERROR("Failed to bind socket '%s': %s\n", name, strerror(errno));
- goto out_unlink;
- }
+ savederrno = errno;
setfscreatecon(NULL);
freecon(filecon);
- chown(addr.sun_path, uid, gid);
- chmod(addr.sun_path, perm);
+ if (ret) {
+ ERROR("Failed to bind socket '%s': %s\n", name, strerror(savederrno));
+ goto out_unlink;
+ }
+
+ ret = lchown(addr.sun_path, uid, gid);
+ if (ret) {
+ ERROR("Failed to lchown socket '%s': %s\n", addr.sun_path, strerror(errno));
+ goto out_unlink;
+ }
+ ret = fchmodat(AT_FDCWD, addr.sun_path, perm, AT_SYMLINK_NOFOLLOW);
+ if (ret) {
+ ERROR("Failed to fchmodat socket '%s': %s\n", addr.sun_path, strerror(errno));
+ goto out_unlink;
+ }
INFO("Created socket '%s' with mode '%o', user '%d', group '%d'\n",
addr.sun_path, perm, uid, gid);