Merge branch 'master' into for-next

2 files changed, 70 insertions, 8 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index dc73bc54cc4e..d9da7e148538 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -39,6 +39,9 @@
 #include <limits.h>
 #include <stddef.h>
 #include <signal.h>
+#include <pwd.h>
+#include <grp.h>
+
 #include <linux/virtio_config.h>
 #include <linux/virtio_net.h>
 #include <linux/virtio_blk.h>
@@ -298,20 +301,27 @@ static void *map_zeroed_pages(unsigned int num)
 
 	/*
 	 * We use a private mapping (ie. if we write to the page, it will be
-	 * copied).
+	 * copied). We allocate an extra two pages PROT_NONE to act as guard
+	 * pages against read/write attempts that exceed allocated space.
 	 */
-	addr = mmap(NULL, getpagesize() * num,
-		    PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
+	addr = mmap(NULL, getpagesize() * (num+2),
+		    PROT_NONE, MAP_PRIVATE, fd, 0);
+
 	if (addr == MAP_FAILED)
 		err(1, "Mmapping %u pages of /dev/zero", num);
 
+	if (mprotect(addr + getpagesize(), getpagesize() * num,
+		     PROT_READ|PROT_WRITE) == -1)
+		err(1, "mprotect rw %u pages failed", num);
+
 	/*
 	 * One neat mmap feature is that you can close the fd, and it
 	 * stays mapped.
 	 */
 	close(fd);
 
-	return addr;
+	/* Return address after PROT_NONE page */
+	return addr + getpagesize();
 }
 
 /* Get some more pages for a device. */
@@ -343,7 +353,7 @@ static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
 	 * done to it.  This allows us to share untouched memory between
 	 * Guests.
 	 */
-	if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
+	if (mmap(addr, len, PROT_READ|PROT_WRITE,
 		 MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
 		return;
 
@@ -573,10 +583,10 @@ static void *_check_pointer(unsigned long addr, unsigned int size,
 			    unsigned int line)
 {
 	/*
-	 * We have to separately check addr and addr+size, because size could
-	 * be huge and addr + size might wrap around.
+	 * Check if the requested address and size exceeds the allocated memory,
+	 * or addr + size wraps around.
 	 */
-	if (addr >= guest_limit || addr + size >= guest_limit)
+	if ((addr + size) > guest_limit || (addr + size) < addr)
 		errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
 	/*
 	 * We return a pointer for the caller's convenience, now we know it's
@@ -1872,6 +1882,8 @@ static struct option opts[] = {
 	{ "block", 1, NULL, 'b' },
 	{ "rng", 0, NULL, 'r' },
 	{ "initrd", 1, NULL, 'i' },
+	{ "username", 1, NULL, 'u' },
+	{ "chroot", 1, NULL, 'c' },
 	{ NULL },
 };
 static void usage(void)
@@ -1894,6 +1906,12 @@ int main(int argc, char *argv[])
 	/* If they specify an initrd file to load. */
 	const char *initrd_name = NULL;
 
+	/* Password structure for initgroups/setres[gu]id */
+	struct passwd *user_details = NULL;
+
+	/* Directory to chroot to */
+	char *chroot_path = NULL;
+
 	/* Save the args: we "reboot" by execing ourselves again. */
 	main_args = argv;
 
@@ -1950,6 +1968,14 @@ int main(int argc, char *argv[])
 		case 'i':
 			initrd_name = optarg;
 			break;
+		case 'u':
+			user_details = getpwnam(optarg);
+			if (!user_details)
+				err(1, "getpwnam failed, incorrect username?");
+			break;
+		case 'c':
+			chroot_path = optarg;
+			break;
 		default:
 			warnx("Unknown argument %s", argv[optind]);
 			usage();
@@ -2021,6 +2047,37 @@ int main(int argc, char *argv[])
 	/* If we exit via err(), this kills all the threads, restores tty. */
 	atexit(cleanup_devices);
 
+	/* If requested, chroot to a directory */
+	if (chroot_path) {
+		if (chroot(chroot_path) != 0)
+			err(1, "chroot(\"%s\") failed", chroot_path);
+
+		if (chdir("/") != 0)
+			err(1, "chdir(\"/\") failed");
+
+		verbose("chroot done\n");
+	}
+
+	/* If requested, drop privileges */
+	if (user_details) {
+		uid_t u;
+		gid_t g;
+
+		u = user_details->pw_uid;
+		g = user_details->pw_gid;
+
+		if (initgroups(user_details->pw_name, g) != 0)
+			err(1, "initgroups failed");
+
+		if (setresgid(g, g, g) != 0)
+			err(1, "setresgid failed");
+
+		if (setresuid(u, u, u) != 0)
+			err(1, "setresuid failed");
+
+		verbose("Dropping privileges completed\n");
+	}
+
 	/* Finally, run the Guest.  This doesn't return. */
 	run_guest();
 }
diff --git a/Documentation/lguest/lguest.txt b/Documentation/lguest/lguest.txt
index 6ccaf8e1a00e..dad99978a6a8 100644
--- a/Documentation/lguest/lguest.txt
+++ b/Documentation/lguest/lguest.txt
@@ -117,6 +117,11 @@ Running Lguest:
     
   for general information on how to get bridging to work.
 
+- Random number generation. Using the --rng option will provide a
+  /dev/hwrng in the guest that will read from the host's /dev/random.
+  Use this option in conjunction with rng-tools (see ../hw_random.txt)
+  to provide entropy to the guest kernel's /dev/random.
+
 There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest
 
 Good luck!