Extend the help with the latest Landlock ABI version supported by the sandboxer. Inform users about the sandboxer or the kernel not being up-to-date. Make the version check code easier to update and harder to misuse. Cc: Günther Noack <gnoack3000@xxxxxxxxx> Cc: Paul Moore <paul@xxxxxxxxxxxxxx> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20220923154207.3311629-2-mic@xxxxxxxxxxx --- samples/landlock/sandboxer.c | 37 ++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 3e404e51ec64..f29bb3c72230 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -162,11 +162,10 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, LANDLOCK_ACCESS_FS_MAKE_SYM | \ LANDLOCK_ACCESS_FS_REFER) -#define ACCESS_ABI_2 ( \ - LANDLOCK_ACCESS_FS_REFER) - /* clang-format on */ +#define LANDLOCK_ABI_LAST 2 + int main(const int argc, char *const argv[], char *const *const envp) { const char *cmd_path; @@ -196,8 +195,12 @@ int main(const int argc, char *const argv[], char *const *const envp) "\nexample:\n" "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" " "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " - "%s bash -i\n", + "%s bash -i\n\n", ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]); + fprintf(stderr, + "This sandboxer can use Landlock features " + "up to ABI version %d.\n", + LANDLOCK_ABI_LAST); return 1; } @@ -225,12 +228,30 @@ int main(const int argc, char *const argv[], char *const *const envp) } return 1; } + /* Best-effort security. */ - if (abi < 2) { - ruleset_attr.handled_access_fs &= ~ACCESS_ABI_2; - access_fs_ro &= ~ACCESS_ABI_2; - access_fs_rw &= ~ACCESS_ABI_2; + switch (abi) { + case 1: + /* Removes LANDLOCK_ACCESS_FS_REFER for ABI < 2 */ + ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_REFER; + + fprintf(stderr, + "Hint: You should update the running kernel " + "to leverage Landlock features " + "provided by ABI version %d (instead of %d).\n", + LANDLOCK_ABI_LAST, abi); + __attribute__((fallthrough)); + case LANDLOCK_ABI_LAST: + break; + default: + fprintf(stderr, + "Hint: You should update this sandboxer " + "to leverage Landlock features " + "provided by ABI version %d (instead of %d).\n", + abi, LANDLOCK_ABI_LAST); } + access_fs_ro &= ruleset_attr.handled_access_fs; + access_fs_rw &= ruleset_attr.handled_access_fs; ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); -- 2.37.2
