Fix dumping hugetlb-based memfd on kernels < 4.16.

4.15-based kernels don't allow F_*SEAL for memfds created with MFD_HUGETLB. Since seals are not possible in this case, fake F_GETSEALS result as if it was queried for a non-sealing-enabled memfd. Signed-off-by: Michał Mirosław <emmir@google.com>
checkpoint-restore · Jun 15, 2023 · af0e413 · af0e413
1 parent 4d137b8
commit af0e413
Showing 1 changed file with 11 additions and 2 deletions.
diff --git a/criu/memfd.c b/criu/memfd.c
@@ -93,8 +93,17 @@ static int dump_memfd_inode(int fd, struct memfd_dump_inode *inode, const char *
 	}
 
 	mie.seals = fcntl(fd, F_GET_SEALS);
-	if (mie.seals == -1)
-		goto out;
+	if (mie.seals == -1) {
+		if (errno != EINVAL || ~mie.hugetlb_flag & MFD_HUGETLB) {
+			pr_perror("fcntl(F_GET_SEALS)");
+			goto out;
+		}
+		/* Kernels before 4.16 don't allow MFD_HUGETLB |
+		 * MFD_ALLOW_SEALING and return EINVAL for
+		 * fcntl(MFD_HUGETLB-enabled fd).
+		 */
+		mie.seals = F_SEAL_SEAL;
+	}
 
 	if (pb_write_one(img_from_set(glob_imgset, CR_FD_MEMFD_INODE), &mie, PB_MEMFD_INODE))
 		goto out;