[LTP] [PATCH v10 0/2] open16: allow restricted O_CREAT of FIFOs and regular files

[LTP] [PATCH v10 0/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao via ltp]

v9->v10:
- Update comments for tst_get_free_uid
- Update logic of tst_get_free_uid

Wei Gao (2):
  lib: New library function tst_get_free_uid
  open16: allow restricted O_CREAT of FIFOs and regular files

 include/tst_uid.h                         |  27 ++++-
 lib/tst_uid.c                             |  28 +++++
 runtest/syscalls                          |   1 +
 testcases/kernel/syscalls/open/.gitignore |   1 +
 testcases/kernel/syscalls/open/open16.c   | 134 ++++++++++++++++++++++
 5 files changed, 187 insertions(+), 4 deletions(-)
 create mode 100644 testcases/kernel/syscalls/open/open16.c

-- 
2.54.0


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[LTP] [PATCH v10 1/2] lib: New library function tst_get_free_uid

[Wei Gao via ltp]

Add tst_get_free_uid() to dynamically find unused UIDs for tests.

Some tests need a completely unassigned, unused UID. This is used by
open16 to verify restricted O_CREAT in sticky directories by running
as a sandboxed user with no file ownership or privileges.

Signed-off-by: Wei Gao <wegao@suse.com>
---
 include/tst_uid.h | 27 +++++++++++++++++++++++----
 lib/tst_uid.c     | 28 ++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/include/tst_uid.h b/include/tst_uid.h
index 2237ddcbf..2ffe84613 100644
--- a/include/tst_uid.h
+++ b/include/tst_uid.h
@@ -7,10 +7,29 @@
 
 #include <sys/types.h>
 
-/*
- * Find unassigned gid. The skip argument can be used to ignore e.g. the main
- * group of a specific user in case it's not listed in the group file. If you
- * do not need to skip any specific gid, simply set it to 0.
+/**
+ * tst_get_free_uid() - Find a UID not assigned to any user.
+ * @skip: UID value to skip (pass 0 to skip none).
+ *
+ * Scans the password database for the first unused UID starting
+ * from 1, skipping @skip. Calls tst_brk(TBROK) if no free UID
+ * is found or a lookup error occurs.
+ *
+ * Return: An unused uid_t value.
+ */
+uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip);
+#define tst_get_free_uid(skip) tst_get_free_uid_(__FILE__, __LINE__, (skip))
+
+/**
+ * tst_get_free_gid() - Find a GID not assigned to any group.
+ * @skip: GID value to skip (pass 0 to skip none).
+ *
+ * Scans the group database for the first unused GID starting from 1,
+ * skipping @skip. The @skip argument can be used to ignore e.g. the main
+ * group of a specific user in case it's not listed in the group file.
+ * Calls tst_brk(TBROK) if no free GID is found or a lookup error occurs.
+ *
+ * Return: An unused gid_t value.
  */
 gid_t tst_get_free_gid_(const char *file, const int lineno, gid_t skip);
 #define tst_get_free_gid(skip) tst_get_free_gid_(__FILE__, __LINE__, (skip))
diff --git a/lib/tst_uid.c b/lib/tst_uid.c
index af4ef8cf7..93c9b83d2 100644
--- a/lib/tst_uid.c
+++ b/lib/tst_uid.c
@@ -5,6 +5,7 @@
 
 #include <sys/types.h>
 #include <grp.h>
+#include <pwd.h>
 #include <errno.h>
 
 #define TST_NO_DEFAULT_MAIN
@@ -12,6 +13,33 @@
 #include "tst_uid.h"
 
 #define MAX_GID 32767
+#define MAX_UID 32767
+
+uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip)
+{
+	uid_t ret;
+
+	for (ret = 1; ret < MAX_UID; ret++) {
+		if (ret == skip)
+			continue;
+
+		errno = 0;
+		if (getpwuid(ret))
+			continue;
+
+		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
+			tst_res_(file, lineno, TINFO | TERRNO,
+				"Found unused UID %d", (int)ret);
+			return ret;
+		}
+
+		tst_brk_(file, lineno, TBROK | TERRNO, "User ID lookup failed");
+		return (uid_t)-1;
+	}
+
+	tst_brk_(file, lineno, TBROK, "No free user ID found");
+	return (uid_t)-1;
+}
 
 gid_t tst_get_free_gid_(const char *file, const int lineno, gid_t skip)
 {
-- 
2.54.0


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Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] lib: New library function tst_get_free_uid

[linuxtestproject.agent]

Hi Wei,

On Tue, 7 Jul 2026 05:47:53 +0000, Wei Gao wrote:
> lib: New library function tst_get_free_uid

--- [PATCH 1/2] ---

> +/**
> + * tst_get_free_uid() - Find a UID not assigned to any user.
> + * @skip: UID value to skip (pass 0 to skip none).

The summary line says tst_get_free_uid() but the symbol being declared
is tst_get_free_uid_(). linuxdoc requires the summary name to match the
symbol exactly, so it would fail to associate this /** block with the
implementation.

Should this be "tst_get_free_uid_() - ..." to match the symbol, or is
the intent to document the macro tst_get_free_uid() instead?

Same issue applies to the modified tst_get_free_gid() summary below.

> +uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip);

The function has three parameters but the kernel-doc block only documents
@skip. linuxdoc expects an @name: entry for every parameter in declaration
order. @file and @lineno are missing.

Same gap in the modified tst_get_free_gid_() block.

> +		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
> +			tst_res_(file, lineno, TINFO | TERRNO,
> +				"Found unused UID %d", (int)ret);
> +			return ret;

When getpwuid() returns NULL with errno set to ENOENT or ESRCH, TERRNO
appends the errno string to the message, producing output like:
"Found unused UID 5: No such file or directory". The function succeeded,
so the error string is misleading. Should TERRNO be dropped here, or
should it be conditionally omitted when errno indicates "not found"?

--- [PATCH 2/2] ---

> +Add LTP coverage for kernel commit 30aba6656f61 (Linux 4.19), which
> +introduced protection against spoofing attacks via O_CREAT of FIFOs and
> +regular files in world-writable sticky directories.
> +
> +This commit adds test cases to verify these security restrictions for
> +opening FIFOs and regular files in world-writable sticky directories.

tcase[2] uses dir_mode=0030|SVTX (group-writable sticky, level 2), which
the commit body doesn't mention. The test's own doc block describes both
"world-writable (level 1) or group-writable (level 2)" correctly — does
the body need updating to match?

Verdict - Needs revision

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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[LTP] [PATCH v11 0/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao via ltp]

v10->v11:
   * tst_uid.h: Moved kernel-doc comments above the macros to fix parser warnings.
   * tst_uid.c: Removed TERRNO from tst_get_free_gid_ success path to avoid misleading output.
   * open16: Added group-writable sticky directories to the commit message to match the test.

Wei Gao (2):
  lib: New library function tst_get_free_uid
  open16: allow restricted O_CREAT of FIFOs and regular files

 include/tst_uid.h                         |  29 ++++-
 lib/tst_uid.c                             |  30 ++++-
 runtest/syscalls                          |   1 +
 testcases/kernel/syscalls/open/.gitignore |   1 +
 testcases/kernel/syscalls/open/open16.c   | 135 ++++++++++++++++++++++
 5 files changed, 191 insertions(+), 5 deletions(-)
 create mode 100644 testcases/kernel/syscalls/open/open16.c

-- 
2.54.0


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[LTP] [PATCH v11 1/2] lib: New library function tst_get_free_uid

[Wei Gao via ltp]

Add tst_get_free_uid() to dynamically find unused UIDs for tests.

Some tests need a completely unassigned, unused UID. This is used by
open16 to verify restricted O_CREAT in sticky directories by running
as a sandboxed user with no file ownership or privileges.

Signed-off-by: Wei Gao <wegao@suse.com>
---
 include/tst_uid.h | 29 +++++++++++++++++++++++++----
 lib/tst_uid.c     | 30 +++++++++++++++++++++++++++++-
 2 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/include/tst_uid.h b/include/tst_uid.h
index 2237ddcbf..c73450956 100644
--- a/include/tst_uid.h
+++ b/include/tst_uid.h
@@ -7,12 +7,33 @@
 
 #include <sys/types.h>
 
-/*
- * Find unassigned gid. The skip argument can be used to ignore e.g. the main
- * group of a specific user in case it's not listed in the group file. If you
- * do not need to skip any specific gid, simply set it to 0.
+uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip);
+
+/**
+ * tst_get_free_uid() - Find a UID not assigned to any user.
+ * @skip: UID value to skip (pass 0 to skip none).
+ *
+ * Scans the password database for the first unused UID starting
+ * from 1, skipping @skip. Calls tst_brk(TBROK) if no free UID
+ * is found or a lookup error occurs.
+ *
+ * Return: An unused uid_t value.
  */
+#define tst_get_free_uid(skip) tst_get_free_uid_(__FILE__, __LINE__, (skip))
+
 gid_t tst_get_free_gid_(const char *file, const int lineno, gid_t skip);
+
+/**
+ * tst_get_free_gid() - Find a GID not assigned to any group.
+ * @skip: GID value to skip (pass 0 to skip none).
+ *
+ * Scans the group database for the first unused GID starting from 1,
+ * skipping @skip. The @skip argument can be used to ignore e.g. the main
+ * group of a specific user in case it's not listed in the group file.
+ * Calls tst_brk(TBROK) if no free GID is found or a lookup error occurs.
+ *
+ * Return: An unused gid_t value.
+ */
 #define tst_get_free_gid(skip) tst_get_free_gid_(__FILE__, __LINE__, (skip))
 
 /*
diff --git a/lib/tst_uid.c b/lib/tst_uid.c
index af4ef8cf7..47c267bc4 100644
--- a/lib/tst_uid.c
+++ b/lib/tst_uid.c
@@ -5,6 +5,7 @@
 
 #include <sys/types.h>
 #include <grp.h>
+#include <pwd.h>
 #include <errno.h>
 
 #define TST_NO_DEFAULT_MAIN
@@ -12,6 +13,33 @@
 #include "tst_uid.h"
 
 #define MAX_GID 32767
+#define MAX_UID 32767
+
+uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip)
+{
+	uid_t ret;
+
+	for (ret = 1; ret < MAX_UID; ret++) {
+		if (ret == skip)
+			continue;
+
+		errno = 0;
+		if (getpwuid(ret))
+			continue;
+
+		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
+			tst_res_(file, lineno, TINFO,
+				"Found unused UID %d", (int)ret);
+			return ret;
+		}
+
+		tst_brk_(file, lineno, TBROK | TERRNO, "User ID lookup failed");
+		return (uid_t)-1;
+	}
+
+	tst_brk_(file, lineno, TBROK, "No free user ID found");
+	return (uid_t)-1;
+}
 
 gid_t tst_get_free_gid_(const char *file, const int lineno, gid_t skip)
 {
@@ -24,7 +52,7 @@ gid_t tst_get_free_gid_(const char *file, const int lineno, gid_t skip)
 			continue;
 
 		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
-			tst_res_(file, lineno, TINFO | TERRNO,
+			tst_res_(file, lineno, TINFO,
 				"Found unused GID %d", (int)ret);
 			return ret;
 		}
-- 
2.54.0


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Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] lib: New library function tst_get_free_uid

[linuxtestproject.agent]

Hi Wei,

On Tue, 21 Jul 2026 07:41:28 +0000, Wei Gao wrote:
> lib: New library function tst_get_free_uid

--- [PATCH 1/2] ---

> -		tst_res_(file, lineno, TINFO | TERRNO,
> +		tst_res_(file, lineno, TINFO,
>  			"Found unused GID %d", (int)ret);

This hunk is a fix to the existing tst_get_free_gid_() success path --
removing | TERRNO so errno is not printed when a free GID is found.

That is a reasonable fix on its own, but it has no relationship to the
new tst_get_free_uid() API that the commit message describes. The commit
message does not mention it.

Could these be split into two patches?

  1/3  lib/tst_uid: Remove spurious TERRNO from tst_get_free_gid success path
  2/3  lib: New library function tst_get_free_uid
  3/3  open16: allow restricted O_CREAT of FIFOs and regular files

Verdict - Needs revision

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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[LTP] [PATCH v11 2/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao via ltp]

Add LTP coverage for kernel commit 30aba6656f61 (Linux 4.19), which
introduced protection against spoofing attacks via O_CREAT of FIFOs and
regular files in world-writable or group-writable sticky directories.

This commit adds test cases to verify these security restrictions (Level 1
and Level 2 protections) for opening FIFOs and regular files in world-writable
or group-writable sticky directories when the file is not owned by the opener.

Signed-off-by: Wei Gao <wegao@suse.com>
---
 runtest/syscalls                          |   1 +
 testcases/kernel/syscalls/open/.gitignore |   1 +
 testcases/kernel/syscalls/open/open16.c   | 135 ++++++++++++++++++++++
 3 files changed, 137 insertions(+)
 create mode 100644 testcases/kernel/syscalls/open/open16.c

diff --git a/runtest/syscalls b/runtest/syscalls
index a021c79da..4fd62efa8 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1008,6 +1008,7 @@ open12 open12
 open13 open13
 open14 open14
 open15 open15
+open16 open16
 
 openat01 openat01
 openat02 openat02
diff --git a/testcases/kernel/syscalls/open/.gitignore b/testcases/kernel/syscalls/open/.gitignore
index af5997572..d2cacc02e 100644
--- a/testcases/kernel/syscalls/open/.gitignore
+++ b/testcases/kernel/syscalls/open/.gitignore
@@ -13,3 +13,4 @@
 /open13
 /open14
 /open15
+/open16
diff --git a/testcases/kernel/syscalls/open/open16.c b/testcases/kernel/syscalls/open/open16.c
new file mode 100644
index 000000000..c74601032
--- /dev/null
+++ b/testcases/kernel/syscalls/open/open16.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Wei Gao <wegao@suse.com>
+ */
+
+/*\
+ * Verify restricted opening (:manpage:`open(2)` and :manpage:`openat(2)`) of
+ * FIFOs and regular files in sticky directories. This test covers the positive
+ * case where access is allowed when protection is disabled (level 0), and the
+ * negative cases where access is disallowed (EACCES) in world-writable (level
+ * 1) or group-writable (level 2) sticky directories when the file is not owned
+ * by the opener.
+ *
+ * This test requires root to modify /proc/sys/fs/protected_* sysctls and
+ * to manage file ownership and permissions in sticky directories.
+ */
+
+#include <pwd.h>
+#include <stdlib.h>
+#include "tst_test.h"
+#include "tst_safe_file_at.h"
+#include "tst_uid.h"
+
+#define DIR "ltp_tmp_check1"
+#define TEST_FILE "test_file_1"
+#define TEST_FIFO "test_fifo_1"
+#define PROTECTED_REGULAR "/proc/sys/fs/protected_regular"
+#define PROTECTED_FIFOS "/proc/sys/fs/protected_fifos"
+#define TEST_FIFO_PATH DIR "/" TEST_FIFO
+
+static int dir_fd = -1;
+static uid_t uid1, uid2;
+static gid_t gid1;
+
+static struct tcase {
+	char *level;
+	int exp_errno;
+	uid_t owner_uid;
+	int use_nobody_gid;
+	mode_t dir_mode;
+} tcases[] = {
+	{"0", 0,      0,  0, 0777 | S_ISVTX},
+	{"1", EACCES, 0,  0, 0777 | S_ISVTX},
+	{"2", EACCES, -1, 1, 0030 | S_ISVTX},
+};
+
+static void verify_open(unsigned int n)
+{
+	struct tcase *tc = &tcases[n];
+	pid_t pid;
+
+	SAFE_FILE_PRINTF(PROTECTED_REGULAR, "%s", tc->level);
+	SAFE_FILE_PRINTF(PROTECTED_FIFOS, "%s", tc->level);
+
+	if (tc->owner_uid != (uid_t)-1 || tc->use_nobody_gid) {
+		gid_t gid = tc->use_nobody_gid ? gid1 : 0;
+
+		SAFE_CHOWN(DIR, tc->owner_uid, gid);
+	}
+
+	if (tc->dir_mode)
+		SAFE_CHMOD(DIR, tc->dir_mode);
+
+	pid = SAFE_FORK();
+	if (!pid) {
+		SAFE_SETGID(gid1);
+		SAFE_SETUID(uid2);
+
+		if (tc->exp_errno) {
+			TST_EXP_FAIL2(openat(dir_fd, TEST_FILE, O_RDWR | O_CREAT, 0777),
+				      tc->exp_errno, "openat %s (Level %s)", TEST_FILE, tc->level);
+			TST_EXP_FAIL2(open(TEST_FIFO_PATH, O_RDWR | O_CREAT, 0777),
+				      tc->exp_errno, "open %s (Level %s)", TEST_FIFO, tc->level);
+		} else {
+			int fd = TST_EXP_FD(openat(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777));
+
+			if (TST_PASS)
+				SAFE_CLOSE(fd);
+
+			fd = TST_EXP_FD(open(TEST_FIFO_PATH, O_RDWR | O_CREAT, 0777));
+			if (TST_PASS)
+				SAFE_CLOSE(fd);
+		}
+
+		exit(0);
+	}
+
+	SAFE_WAITPID(pid, NULL, 0);
+}
+
+static void setup(void)
+{
+	struct passwd *pw;
+
+	pw = SAFE_GETPWNAM("nobody");
+	uid1 = pw->pw_uid;
+	gid1 = pw->pw_gid;
+	uid2 = tst_get_free_uid(uid1);
+
+	umask(0);
+	SAFE_MKDIR(DIR, 0777 | S_ISVTX);
+	dir_fd = SAFE_OPEN(DIR, O_DIRECTORY);
+
+	int fd = SAFE_OPENAT(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777);
+
+	SAFE_CLOSE(fd);
+	SAFE_MKFIFO(TEST_FIFO_PATH, 0777);
+	SAFE_CHOWN(TEST_FIFO_PATH, uid1, gid1);
+	SAFE_CHOWN(DIR "/" TEST_FILE, uid1, gid1);
+}
+
+static void cleanup(void)
+{
+	if (dir_fd != -1)
+		SAFE_CLOSE(dir_fd);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.needs_root = 1,
+	.tcnt = ARRAY_SIZE(tcases),
+	.test = verify_open,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.save_restore = (const struct tst_path_val[]) {
+		{PROTECTED_REGULAR, NULL, TST_SR_TCONF},
+		{PROTECTED_FIFOS, NULL, TST_SR_TCONF},
+		{}
+	},
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "30aba6656f61"},
+		{}
+	}
+};
-- 
2.54.0


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Re: [LTP] [PATCH v11 0/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Andrea Cervesato via ltp]

Hi Wei,

can you please send the patch-set in a new thread, instead of replying
to the old version? we are having a really long thread in the lore
instance and it's getting diffciult to read.

https://lore.kernel.org/ltp/20250516151028.1254207-1-wegao@suse.com/

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

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Re: [LTP] [PATCH v11 0/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao via ltp]

Hi Andrea

Ok, I will send it in a new thread.

Thanks.

Gao Wei

On Tue, Jul 21, 2026 at 4:23 PM Andrea Cervesato <andrea.cervesato@suse.com>
wrote:

> Hi Wei,
>
> can you please send the patch-set in a new thread, instead of replying
> to the old version? we are having a really long thread in the lore
> instance and it's getting diffciult to read.
>
> https://lore.kernel.org/ltp/20250516151028.1254207-1-wegao@suse.com/
>
> Thanks,
> --
> Andrea Cervesato
> SUSE QE Automation Engineer Linux
> andrea.cervesato@suse.com
>

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[LTP] [PATCH v10 2/2] open16: allow restricted O_CREAT of FIFOs and regular files

[Wei Gao via ltp]

Add LTP coverage for kernel commit 30aba6656f61 (Linux 4.19), which
introduced protection against spoofing attacks via O_CREAT of FIFOs and
regular files in world-writable sticky directories.

This commit adds test cases to verify these security restrictions for
opening FIFOs and regular files in world-writable sticky directories.

Signed-off-by: Wei Gao <wegao@suse.com>
---
 runtest/syscalls                          |   1 +
 testcases/kernel/syscalls/open/.gitignore |   1 +
 testcases/kernel/syscalls/open/open16.c   | 134 ++++++++++++++++++++++
 3 files changed, 136 insertions(+)
 create mode 100644 testcases/kernel/syscalls/open/open16.c

diff --git a/runtest/syscalls b/runtest/syscalls
index a021c79da..4fd62efa8 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1008,6 +1008,7 @@ open12 open12
 open13 open13
 open14 open14
 open15 open15
+open16 open16
 
 openat01 openat01
 openat02 openat02
diff --git a/testcases/kernel/syscalls/open/.gitignore b/testcases/kernel/syscalls/open/.gitignore
index af5997572..d2cacc02e 100644
--- a/testcases/kernel/syscalls/open/.gitignore
+++ b/testcases/kernel/syscalls/open/.gitignore
@@ -13,3 +13,4 @@
 /open13
 /open14
 /open15
+/open16
diff --git a/testcases/kernel/syscalls/open/open16.c b/testcases/kernel/syscalls/open/open16.c
new file mode 100644
index 000000000..2e45d7f12
--- /dev/null
+++ b/testcases/kernel/syscalls/open/open16.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Wei Gao <wegao@suse.com>
+ */
+
+/*\
+ * Verify restricted opening of FIFOs and regular files in sticky directories.
+ * This test covers the positive case where access is allowed when protection
+ * is disabled (level 0), and the negative cases where access is disallowed
+ * (EACCES) in world-writable (level 1) or group-writable (level 2) sticky
+ * directories when the file is not owned by the opener.
+ *
+ * This test requires root to modify /proc/sys/fs/protected_* sysctls and
+ * to manage file ownership and permissions in sticky directories.
+ */
+
+#include <pwd.h>
+#include <stdlib.h>
+#include "tst_test.h"
+#include "tst_safe_file_at.h"
+#include "tst_uid.h"
+
+#define DIR "ltp_tmp_check1"
+#define TEST_FILE "test_file_1"
+#define TEST_FIFO "test_fifo_1"
+#define PROTECTED_REGULAR "/proc/sys/fs/protected_regular"
+#define PROTECTED_FIFOS "/proc/sys/fs/protected_fifos"
+#define TEST_FIFO_PATH DIR "/" TEST_FIFO
+
+static int dir_fd = -1;
+static uid_t uid1, uid2;
+static gid_t gid1;
+
+static struct tcase {
+	char *level;
+	int exp_errno;
+	uid_t owner_uid;
+	int use_nobody_gid;
+	mode_t dir_mode;
+} tcases[] = {
+	{"0", 0,      0,  0, 0777 | S_ISVTX},
+	{"1", EACCES, 0,  0, 0777 | S_ISVTX},
+	{"2", EACCES, -1, 1, 0030 | S_ISVTX},
+};
+
+static void verify_open(unsigned int n)
+{
+	struct tcase *tc = &tcases[n];
+	pid_t pid;
+
+	SAFE_FILE_PRINTF(PROTECTED_REGULAR, "%s", tc->level);
+	SAFE_FILE_PRINTF(PROTECTED_FIFOS, "%s", tc->level);
+
+	if (tc->owner_uid != (uid_t)-1 || tc->use_nobody_gid) {
+		gid_t gid = tc->use_nobody_gid ? gid1 : 0;
+
+		SAFE_CHOWN(DIR, tc->owner_uid, gid);
+	}
+
+	if (tc->dir_mode)
+		SAFE_CHMOD(DIR, tc->dir_mode);
+
+	pid = SAFE_FORK();
+	if (!pid) {
+		SAFE_SETGID(gid1);
+		SAFE_SETUID(uid2);
+
+		if (tc->exp_errno) {
+			TST_EXP_FAIL2(openat(dir_fd, TEST_FILE, O_RDWR | O_CREAT, 0777),
+				      tc->exp_errno, "openat %s (Level %s)", TEST_FILE, tc->level);
+			TST_EXP_FAIL2(open(TEST_FIFO_PATH, O_RDWR | O_CREAT, 0777),
+				      tc->exp_errno, "open %s (Level %s)", TEST_FIFO, tc->level);
+		} else {
+			int fd = TST_EXP_FD(openat(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777));
+
+			if (TST_PASS)
+				SAFE_CLOSE(fd);
+
+			fd = TST_EXP_FD(open(TEST_FIFO_PATH, O_RDWR | O_CREAT, 0777));
+			if (TST_PASS)
+				SAFE_CLOSE(fd);
+		}
+
+		exit(0);
+	}
+
+	SAFE_WAITPID(pid, NULL, 0);
+}
+
+static void setup(void)
+{
+	struct passwd *pw;
+
+	pw = SAFE_GETPWNAM("nobody");
+	uid1 = pw->pw_uid;
+	gid1 = pw->pw_gid;
+	uid2 = tst_get_free_uid(uid1);
+
+	umask(0);
+	SAFE_MKDIR(DIR, 0777 | S_ISVTX);
+	dir_fd = SAFE_OPEN(DIR, O_DIRECTORY);
+
+	int fd = SAFE_OPENAT(dir_fd, TEST_FILE, O_CREAT | O_RDWR, 0777);
+
+	SAFE_CLOSE(fd);
+	SAFE_MKFIFO(TEST_FIFO_PATH, 0777);
+	SAFE_CHOWN(TEST_FIFO_PATH, uid1, gid1);
+	SAFE_CHOWN(DIR "/" TEST_FILE, uid1, gid1);
+}
+
+static void cleanup(void)
+{
+	if (dir_fd != -1)
+		SAFE_CLOSE(dir_fd);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.needs_root = 1,
+	.tcnt = ARRAY_SIZE(tcases),
+	.test = verify_open,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.save_restore = (const struct tst_path_val[]) {
+		{PROTECTED_REGULAR, NULL, TST_SR_TCONF},
+		{PROTECTED_FIFOS, NULL, TST_SR_TCONF},
+		{}
+	},
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "30aba6656f61"},
+		{}
+	}
+};
-- 
2.54.0


-- 
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