[LTP] [PATCH v4] inotify13: check rename cookie pairing after adjacent moves
Amir Goldstein
amir73il@gmail.com
Fri Oct 30 10:20:18 CET 2026
On Thu, Oct 29, 2026 at 10:07 PM Hungyu Lin <dennylin0707@gmail.com> wrote:
>
> 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>
Thank you for your patience with my review
Reviewed-by: Amir Goldstein <amir73il@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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