[LTP] lapi: fallback fchroot() parameters

[Andrea Cervesato]

> Hi Andrea,
> 
> On 2026-10-20, Andrea Cervesato wrote:
> > lapi: fallback fchroot() parameters
> 
> --- [PATCH 5/14] ---
> 
> > diff --git a/testcases/kernel/syscalls/fchroot/fchroot04.c b/testcases/kernel/syscalls/fchroot/fchroot04.c
> > +	TST_EXP_PASS(tst_syscall(__NR_fchroot, FD_FAILFS_ROOT, 0),
> > +		"fchroot() with the FD_FAILFS_ROOT sentinel");
> 
> High: Stop the child if this expectation fails; TST_EXP_PASS records a
> failure but continues execution. For example, root without CAP_SYS_CHROOT
> and without no_new_privs gets EPERM, then mkdir("/foo") can create a
> directory in the real root that tmpdir cleanup never removes. Check
> TST_PASS and exit before executing the absolute-path operations.

Valid

> 
> --- [PATCH 6/14] ---
> 
> > diff --git a/testcases/kernel/syscalls/fchroot/fchroot05.c b/testcases/kernel/syscalls/fchroot/fchroot05.c
> > +	len = readlinkat(procfd, "self/root", buf, sizeof(buf) - 1);
> > +	if (len < 0) {
> > +		tst_res(TFAIL | TTERRNO, "readlinkat() of /proc/self/root");
> 
> Low: TTERRNO still reads the preceding fstatat() error from TST_ERR,
> not readlinkat()'s errno. Wrap readlinkat() in TEST() or
> TST_EXP_POSITIVE() so a failure reports the actual error.
> 

Valid

> --- [PATCH 8/14] ---
> 
> > diff --git a/testcases/kernel/syscalls/fchroot/fchroot07.c b/testcases/kernel/syscalls/fchroot/fchroot07.c
> > +	SAFE_WAIT(NULL);
> 
> High: A successfully executed helper can fail in tst_reinit() while
> reopening its absolute IPC pathname under failfs, before it can publish
> TFAIL through shared memory. SAFE_WAIT(NULL) discards that nonzero exit,
> leaving only the earlier fchroot TPASS and a false pass. Use
> tst_reap_children() to retain child-failure detection.
> 
> > +	if (tst_get_path(CHILD_EXEC, child_path, sizeof(child_path)))
> > +		tst_brk(TCONF, "Couldn't find %s in $PATH", CHILD_EXEC);
> 
> Medium: Make child_path absolute before entering failfs. Despite its API
> comment, tst_get_path() returns ./fchroot07_child when the helper is found
> through an empty or relative PATH component, including the empty component
> inserted by the framework when running from the build directory. This
> tests relative execution and, for a dynamic binary, its interpreter lookup
> rather than the claimed absolute executable lookup.

All failfs assumptions don't make any sense, let's skip these.

> 
> --- [PATCH 12/14] ---
> 
> > diff --git a/testcases/kernel/syscalls/fchroot/fchroot11.c b/testcases/kernel/syscalls/fchroot/fchroot11.c
> > +	.needs_kconfigs = (const char *[]) {
> > +		"CONFIG_USER_NS=y",
> > +		NULL,
> > +	}
> 
> Medium: Gate only the user-namespace subcase, not the entire test.
> Unprivileged failfs entry with no_new_privs works without CONFIG_USER_NS,
> but this descriptor skips its success and lookup checks as well. Keep
> those checks enabled and report TCONF only for the unavailable namespace
> subcase.

Valid

> 
> Verdict - Needs revision
> 
> Pre-existing issue: include/tst_fs.h documents tst_get_path() as returning
> an absolute path, but lib/get_path.c preserves relative PATH entries.

This is a documentation bug

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com