[LTP] [PATCH v4] inotify13: check rename cookie pairing after adjacent moves
Hungyu Lin
dennylin0707@gmail.com
Thu Oct 29 22:07:01 CET 2026
Queue an unpaired IN_MOVED_FROM event, followed by an IN_MOVED_FROM and
IN_MOVED_TO pair with the same source watch descriptor and name as the
first event. Watch only IN_MOVE so creation of the replacement entry
does not separate the two IN_MOVED_FROM events in the queue.
Affected kernels coalesce the second IN_MOVED_FROM into the first,
leaving the IN_MOVED_TO cookie without a matching IN_MOVED_FROM cookie.
Check that all three events are retained, the two moves have distinct
cookies, and the second IN_MOVED_FROM matches the IN_MOVED_TO cookie.
Cover both regular files and directories.
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
Changes in v4:
- Put expected values immediately after the mismatched fields, following
the existing per-field diagnostic format.
- Use the existing "got unnecessary event" and "didn't get event" wording.
- Keep event context for extra events and mask, watch descriptor and
filename mismatches. Omit it from the two cookie-failure messages,
since it is already present in TINFO, as confirmed by Amir.
Built with GCC 13.3.0 and checked with LTP checkpatch and sparse. On ARM64
QEMU, the test reports 0 pass / 2 fail on the baseline kernel and 2 pass /
0 fail with the kernel fix. Local diagnostic controls also exercise both
cookie failures and verify the preceding TINFO and concise TFAIL output.
The controls are kept outside this patch.
runtest/syscalls | 1 +
testcases/kernel/syscalls/inotify/.gitignore | 1 +
testcases/kernel/syscalls/inotify/inotify13.c | 211 ++++++++++++++++++++++++++
3 files changed, 213 insertions(+)
create mode 100644 testcases/kernel/syscalls/inotify/inotify13.c
diff --git a/runtest/syscalls b/runtest/syscalls
index 2bdb4a9a2b4801d03d93efea686124530f5ce2d5..e578bd92d7e7ded5c0ca2f95dc87fce814d733cc 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -677,6 +677,7 @@ inotify09 inotify09
inotify10 inotify10
inotify11 inotify11
inotify12 inotify12
+inotify13 inotify13
fanotify01 fanotify01
fanotify02 fanotify02
diff --git a/testcases/kernel/syscalls/inotify/.gitignore b/testcases/kernel/syscalls/inotify/.gitignore
index f6e5c546ac4032766cee9f16b3689be5d0302d37..b597ea63f493b2da2a58017d3eb7b16a7b033fc5 100644
--- a/testcases/kernel/syscalls/inotify/.gitignore
+++ b/testcases/kernel/syscalls/inotify/.gitignore
@@ -10,3 +10,4 @@
/inotify10
/inotify11
/inotify12
+/inotify13
diff --git a/testcases/kernel/syscalls/inotify/inotify13.c b/testcases/kernel/syscalls/inotify/inotify13.c
new file mode 100644
index 0000000000000000000000000000000000000000..9ee660e041435d16b63097ba8e2f86515d6bac57
--- /dev/null
+++ b/testcases/kernel/syscalls/inotify/inotify13.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Hungyu Lin <dennylin0707@gmail.com>
+ */
+
+/*\
+ * Verify that two IN_MOVED_FROM events that differ only in their rename
+ * cookie are not coalesced.
+ *
+ * inotify(7) allows coalescing only of events with identical wd, mask,
+ * cookie and name. A regression introduced in v2.6.31 dropped the cookie
+ * comparison. On affected kernels, the second IN_MOVED_FROM is coalesced
+ * into the first, leaving the following IN_MOVED_TO without a matching
+ * IN_MOVED_FROM cookie.
+ *
+ * With source/ and target/ watched for IN_MOVE, and without reading the queue:
+ *
+ * 1. Move source/entry to unwatched/ (IN_MOVED_FROM, cookie A).
+ * 2. Recreate source/entry.
+ * 3. Move source/entry to target/ (IN_MOVED_FROM and IN_MOVED_TO, cookie B).
+ *
+ * All three events must be queued, with A != B. IN_CREATE is not watched, so
+ * the two IN_MOVED_FROM events are adjacent; the queue is not read in between,
+ * because only the last unread event can be merged with a new one. Both a
+ * regular file and a directory are tested.
+ */
+
+#include "config.h"
+#include <fcntl.h>
+#include <string.h>
+#include "tst_test.h"
+#include "inotify.h"
+
+#ifdef HAVE_SYS_INOTIFY_H
+#include <sys/inotify.h>
+
+#define SOURCE "source/entry"
+#define UNWATCHED "unwatched/entry"
+#define TARGET "target/entry"
+
+struct event_t {
+ const char *name;
+ unsigned int mask;
+ int wd;
+};
+
+static struct tcase {
+ const char *type;
+ unsigned int isdir;
+} tcases[] = {
+ { "file", 0 },
+ { "directory", IN_ISDIR },
+};
+
+static int fd_notify = -1;
+
+static void create_entry(unsigned int isdir, const char *path)
+{
+ if (isdir)
+ SAFE_MKDIR(path, 0700);
+ else
+ SAFE_TOUCH(path, 0600, NULL);
+}
+
+static void delete_entry(unsigned int isdir, const char *path)
+{
+ if (isdir)
+ SAFE_RMDIR(path);
+ else
+ SAFE_UNLINK(path);
+}
+
+static void verify_inotify(unsigned int n)
+{
+ const char *type = tcases[n].type;
+ unsigned int isdir = tcases[n].isdir;
+ struct event_t event_set[] = {
+ { "entry", IN_MOVED_FROM | isdir, 0 },
+ { "entry", IN_MOVED_FROM | isdir, 0 },
+ { "entry", IN_MOVED_TO | isdir, 0 },
+ };
+ union {
+ struct inotify_event align;
+ char data[4096];
+ } buf;
+ struct inotify_event *event;
+ const struct event_t *expected;
+ unsigned int cookies[ARRAY_SIZE(event_set)] = { 0 };
+ unsigned int count = 0, i;
+ size_t pos = 0, len;
+ int wd_source, wd_target;
+
+ fd_notify = SAFE_MYINOTIFY_INIT1(O_NONBLOCK);
+ wd_source = SAFE_MYINOTIFY_ADD_WATCH(fd_notify, "source", IN_MOVE);
+ wd_target = SAFE_MYINOTIFY_ADD_WATCH(fd_notify, "target", IN_MOVE);
+
+ event_set[0].wd = wd_source;
+ event_set[1].wd = wd_source;
+ event_set[2].wd = wd_target;
+
+ create_entry(isdir, SOURCE);
+ SAFE_RENAME(SOURCE, UNWATCHED);
+ create_entry(isdir, SOURCE);
+ SAFE_RENAME(SOURCE, TARGET);
+
+ len = SAFE_READ(SAFE_READ_ANY_EAGAIN, fd_notify, buf.data, sizeof(buf.data));
+ SAFE_CLOSE(fd_notify);
+
+ /* Reuse these paths for the next case and for -i iterations. */
+ delete_entry(isdir, UNWATCHED);
+ delete_entry(isdir, TARGET);
+
+ while (pos < len) {
+ if (len - pos < sizeof(*event))
+ tst_brk(TBROK, "%s: event %u has %zu header bytes (expected at least %zu)",
+ type, count, len - pos, sizeof(*event));
+
+ event = (struct inotify_event *)(buf.data + pos);
+ if (event->len > len - pos - sizeof(*event))
+ tst_brk(TBROK, "%s: event %u claims %u name bytes but only %zu are left in the buffer, wd=%d mask=%#x cookie=%u",
+ type, count, event->len, len - pos - sizeof(*event),
+ event->wd, event->mask, event->cookie);
+
+ if (count >= ARRAY_SIZE(event_set)) {
+ tst_res(TFAIL, "%s: got unnecessary event %u: mask=%#x wd=%d cookie=%u len=%u name=\"%.*s\"",
+ type, count, event->mask, event->wd, event->cookie,
+ event->len, (int)event->len, event->name);
+ return;
+ }
+
+ expected = &event_set[count];
+ if (event->mask != expected->mask) {
+ tst_res(TFAIL, "%s: got event %u: mask=%#x (expected %#x) wd=%d cookie=%u name=\"%.*s\"",
+ type, count, event->mask, expected->mask, event->wd,
+ event->cookie, (int)event->len, event->name);
+ return;
+ }
+
+ if (event->wd != expected->wd) {
+ tst_res(TFAIL, "%s: got event %u: mask=%#x wd=%d (expected %d) cookie=%u name=\"%.*s\"",
+ type, count, event->mask, event->wd, expected->wd,
+ event->cookie, (int)event->len, event->name);
+ return;
+ }
+
+ if (event->len < strlen(expected->name) + 1 ||
+ strncmp(expected->name, event->name, event->len)) {
+ tst_res(TFAIL, "%s: got event %u: mask=%#x wd=%d cookie=%u len=%u name=\"%.*s\" (expected \"%s\")",
+ type, count, event->mask, event->wd, event->cookie,
+ event->len, (int)event->len, event->name,
+ expected->name);
+ return;
+ }
+
+ cookies[count] = event->cookie;
+ tst_res(TINFO, "%s: event %u: wd=%d mask=%#x cookie=%u len=%u name=\"%.*s\"",
+ type, count, event->wd, event->mask, event->cookie,
+ event->len, (int)event->len, event->name);
+ count++;
+ pos += sizeof(*event) + event->len;
+ }
+
+ for (i = count; i < ARRAY_SIZE(event_set); i++) {
+ expected = &event_set[i];
+ tst_res(TFAIL, "%s: didn't get event %u: mask=%#x wd=%d name=\"%s\"",
+ type, i, expected->mask, expected->wd, expected->name);
+ }
+
+ if (count < ARRAY_SIZE(event_set))
+ return;
+
+ if (cookies[0] == cookies[1]) {
+ tst_res(TFAIL, "%s: got second FROM cookie=%u (expected != %u)",
+ type, cookies[1], cookies[0]);
+ return;
+ }
+
+ if (cookies[1] != cookies[2]) {
+ tst_res(TFAIL, "%s: got TO cookie=%u (expected %u from second FROM)",
+ type, cookies[2], cookies[1]);
+ return;
+ }
+
+ tst_res(TPASS, "%s: FROM cookies %u and %u differ, TO cookie %u matches the second",
+ type, cookies[0], cookies[1], cookies[2]);
+}
+
+static void setup(void)
+{
+ SAFE_MKDIR("source", 0700);
+ SAFE_MKDIR("unwatched", 0700);
+ SAFE_MKDIR("target", 0700);
+}
+
+static void cleanup(void)
+{
+ if (fd_notify >= 0)
+ SAFE_CLOSE(fd_notify);
+}
+
+static struct tst_test test = {
+ .test = verify_inotify,
+ .tcnt = ARRAY_SIZE(tcases),
+ .setup = setup,
+ .cleanup = cleanup,
+ .needs_tmpdir = 1,
+};
+
+#else
+TST_TEST_TCONF("system doesn't have required inotify support");
+#endif
--
2.43.0
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