[LTP] [PATCH] migrate_pages02: update for 4.15

[Jan Stancek]

commit 313674661925 ("Unify migrate_pages and move_pages access checks")
tightened checks for unprivileged user. It requires that callers real
uid/gid matches target [es]uig/[es]gid and target to be dumpable
(see __ptrace_may_access()).

It broke the test, because change of only euid is no longer
sufficient.

This patch updates test to use setuid(), which sets all user IDs.
Since we can't change uid back to 0, we fork additional child
process for "caller", which is now free to drop privileges.

This change should be backwards-compatible with kernels < 4.15.
Tested on 4.15-rc6 and 4.14.

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---

Note: So far this is only in 4.15-rcX kernels and could still change before release.

 .../syscalls/migrate_pages/migrate_pages02.c       | 72 ++++++++++++----------
 1 file changed, 41 insertions(+), 31 deletions(-)

diff --git a/testcases/kernel/syscalls/migrate_pages/migrate_pages02.c b/testcases/kernel/syscalls/migrate_pages/migrate_pages02.c
index faf96b6b79ee..8a5ff158c901 100644
--- a/testcases/kernel/syscalls/migrate_pages/migrate_pages02.c
+++ b/testcases/kernel/syscalls/migrate_pages/migrate_pages02.c
@@ -34,6 +34,7 @@
 #include <sys/syscall.h>
 #include <sys/wait.h>
 #include <sys/mman.h>
+#include <sys/prctl.h>
 #include <errno.h>
 #if HAVE_NUMA_H
 #include <numa.h>
@@ -159,12 +160,12 @@ static int check_addr_on_node(void *addr, int exp_node)
 	if (node == exp_node) {
 		tst_resm(TPASS, "pid(%d) addr %p is on expected node: %d",
 			 getpid(), addr, exp_node);
-		return 0;
+		return TPASS;
 	} else {
 		tst_resm(TFAIL, "pid(%d) addr %p not on expected node: %d "
 			 ", expected %d", getpid(), addr, node, exp_node);
 		print_mem_stats(0, exp_node);
-		return 1;
+		return TFAIL;
 	}
 }
 
@@ -235,13 +236,13 @@ static void test_migrate_current_process(int node1, int node2, int cap_sys_nice)
 static void test_migrate_other_process(int node1, int node2, int cap_sys_nice)
 {
 	char *testp;
-	int status, ret, tmp;
-	pid_t child;
-	int child_ready[2];
+	int ret, tmp;
+	pid_t child1, child2;
+	int child1_ready[2];
 	int pages_migrated[2];
 
-	/* setup pipes to synchronize child/parent */
-	if (pipe(child_ready) == -1)
+	/* setup pipes to synchronize child1/child2 */
+	if (pipe(child1_ready) == -1)
 		tst_resm(TBROK | TERRNO, "pipe #1 failed");
 	if (pipe(pages_migrated) == -1)
 		tst_resm(TBROK | TERRNO, "pipe #2 failed");
@@ -249,13 +250,13 @@ static void test_migrate_other_process(int node1, int node2, int cap_sys_nice)
 	tst_resm(TINFO, "other_process, cap_sys_nice: %d", cap_sys_nice);
 
 	fflush(stdout);
-	child = fork();
-	switch (child) {
+	child1 = fork();
+	switch (child1) {
 	case -1:
 		tst_brkm(TBROK | TERRNO, cleanup, "fork");
 		break;
 	case 0:
-		close(child_ready[0]);
+		close(child1_ready[0]);
 		close(pages_migrated[1]);
 
 		testp = SAFE_MALLOC(NULL, getpagesize());
@@ -265,47 +266,56 @@ static void test_migrate_other_process(int node1, int node2, int cap_sys_nice)
 		migrate_to_node(0, node1);
 		check_addr_on_node(testp, node1);
 
-		SAFE_SETEUID(NULL, ltpuser->pw_uid);
+		SAFE_SETUID(NULL, ltpuser->pw_uid);
 
-		/* signal parent it's OK to migrate child and wait */
-		if (write(child_ready[1], &tmp, 1) != 1)
+		/* commit_creds() will clear dumpable, restore it */
+		if (prctl(PR_SET_DUMPABLE, 1))
+			tst_brkm(TBROK | TERRNO, NULL, "prctl");
+
+		/* signal child2 it's OK to migrate child1 and wait */
+		if (write(child1_ready[1], &tmp, 1) != 1)
 			tst_brkm(TBROK | TERRNO, NULL, "write #1 failed");
 		if (read(pages_migrated[0], &tmp, 1) != 1)
 			tst_brkm(TBROK | TERRNO, NULL, "read #1 failed");
 
-		/* parent can migrate child process with same euid */
-		/* parent can migrate child process with CAP_SYS_NICE */
+		/* child2 can migrate child1 process if it's privileged */
+		/* child2 can migrate child1 process if it has same uid */
 		ret = check_addr_on_node(testp, node2);
 
 		free(testp);
-		close(child_ready[1]);
+		close(child1_ready[1]);
 		close(pages_migrated[0]);
 		exit(ret);
-	default:
-		close(child_ready[1]);
-		close(pages_migrated[0]);
+	}
+
+	close(child1_ready[1]);
+	close(pages_migrated[0]);
 
+	fflush(stdout);
+	child2 = fork();
+	switch (child2) {
+	case -1:
+		tst_brkm(TBROK | TERRNO, cleanup, "fork");
+		break;
+	case 0:
 		if (!cap_sys_nice)
-			SAFE_SETEUID(NULL, ltpuser->pw_uid);
+			SAFE_SETUID(NULL, ltpuser->pw_uid);
 
-		/* wait until child is ready on node1, then migrate and
+		/* wait until child1 is ready on node1, then migrate and
 		 * signal to check current node */
-		if (read(child_ready[0], &tmp, 1) != 1)
+		if (read(child1_ready[0], &tmp, 1) != 1)
 			tst_brkm(TBROK | TERRNO, NULL, "read #2 failed");
-		migrate_to_node(child, node2);
+		migrate_to_node(child1, node2);
 		if (write(pages_migrated[1], &tmp, 1) != 1)
 			tst_brkm(TBROK | TERRNO, NULL, "write #2 failed");
 
-		SAFE_WAITPID(cleanup, child, &status, 0);
-		if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
-			tst_resm(TFAIL, "child returns %d", status);
-		close(child_ready[0]);
+		close(child1_ready[0]);
 		close(pages_migrated[1]);
-
-		/* reset euid, so this testcase can be used in loop */
-		if (!cap_sys_nice)
-			SAFE_SETEUID(NULL, 0);
+		exit(TPASS);
 	}
+
+	tst_record_childstatus(NULL, child2);
+	tst_record_childstatus(NULL, child1);
 }
 
 int main(int argc, char *argv[])
-- 
1.8.3.1