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-rw-r--r--samples/landlock/sandboxer.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index fd4237c64fb2..e2056c8b902c 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -234,7 +234,22 @@ int main(const int argc, char *const argv[], char *const *const envp)
/* Best-effort security. */
switch (abi) {
case 1:
- /* Removes LANDLOCK_ACCESS_FS_REFER for ABI < 2 */
+ /*
+ * Removes LANDLOCK_ACCESS_FS_REFER for ABI < 2
+ *
+ * Note: The "refer" operations (file renaming and linking
+ * across different directories) are always forbidden when using
+ * Landlock with ABI 1.
+ *
+ * If only ABI 1 is available, this sandboxer knowingly forbids
+ * refer operations.
+ *
+ * If a program *needs* to do refer operations after enabling
+ * Landlock, it can not use Landlock at ABI level 1. To be
+ * compatible with different kernel versions, such programs
+ * should then fall back to not restrict themselves at all if
+ * the running kernel only supports ABI 1.
+ */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_REFER;
__attribute__((fallthrough));
case 2: