FAILED: patch "[PATCH] io_uring/futex: only mark private futex waits as inflight" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] io_uring/futex: only mark private futex waits as inflight" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 4d327bbd1cd2485783553b6b2b401aa475f90dd0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026082442-slogan-feminine-7a8d@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4d327bbd1cd2485783553b6b2b401aa475f90dd0 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 30 Jul 2026 06:50:47 -0600
Subject: [PATCH] io_uring/futex: only mark private futex waits as inflight

Inflight tracking of futex wait requests exists to ensure that do_exit()
-> io_uring_files_cancel() cancels them before the mm goes away, as a
private futex wait depends on the mm private futex hash staying alive
for the duration of the request.

Shared futexes have no such dependency. A FLAGS_SHARED request always
resolves to either an inode based key or an mm-shared key, both of which
fail futex_key_is_private() and hence always hash into the global futex
hash, whose lifetime isn't tied to the mm.

Only mark vectored futex waits as inflight if the futex is private.

Cc: stable@vger.kernel.org
Fixes: 079afb081c42 ("io_uring/futex: mark wait requests as inflight")
Link: https://lore.kernel.org/io-uring/CANGjgdn=R_qyUdE=j9za+vkmqcxacbP-84OHXF4nZ4ho9qRyVg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/futex.c b/io_uring/futex.c
index eea0425f2bcb..f0d80a444f45 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -154,14 +154,16 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 int io_futex_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
 	int ret;
 
 	ret = io_futex_prep(req, sqe);
 	if (unlikely(ret))
 		return ret;
 
-	/* Mark as inflight, so file exit cancelation will find it */
-	io_req_track_inflight(req);
+	/* inflight tracking only needed for mm private hash */
+	if (!(iof->futex_flags & FLAGS_SHARED))
+		io_req_track_inflight(req);
 	return 0;
 }
 
@@ -186,6 +188,7 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
 	struct io_futexv_data *ifd;
+	unsigned int i;
 	int ret;
 
 	/* No flags or mask supported for waitv */
@@ -210,8 +213,14 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return ret;
 	}
 
-	/* Mark as inflight, so file exit cancelation will find it */
-	io_req_track_inflight(req);
+	/* inflight tracking only needed for mm private hash */
+	for (i = 0; i < iof->futex_nr; i++) {
+		if (!(ifd->futexv[i].w.flags & FLAGS_SHARED)) {
+			io_req_track_inflight(req);
+			break;
+		}
+	}
+
 	iof->futexv_unqueued = 0;
 	req->flags |= REQ_F_ASYNC_DATA;
 	req->async_data = ifd;

[PATCH 6.18.y 1/2] io_uring/futex: don't mark futex wake requests as inflight

[Sasha Levin]

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 73e7019097473fc9f83a334ef2c6ab3343709fef ]

Commit 079afb081c42 ("io_uring/futex: mark wait requests as inflight")
added inflight tracking to ensure that do_exit() ->
io_uring_files_cancel() finds and cancels pending futex waits before the
mm goes away, as a private futex wait depends on the mm private futex
hash staying alive for the duration of the request. However, as
io_futex_prep() is shared between FUTEX_WAIT and FUTEX_WAKE, wake
requests got marked as inflight as well.

A futex wake executes fully inline at issue time and never depends on
the mm staying alive after completion, hence there's no need to track
it. Kill it.

Cc: stable@vger.kernel.org
Fixes: 079afb081c42 ("io_uring/futex: mark wait requests as inflight")
Reported-by: Chengfeng Lin <lin2530632123@gmail.com>
Link: https://lore.kernel.org/io-uring/CANGjgdn=R_qyUdE=j9za+vkmqcxacbP-84OHXF4nZ4ho9qRyVg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: 4d327bbd1cd2 ("io_uring/futex: only mark private futex waits as inflight")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 io_uring/futex.c | 11 +++++++++++
 io_uring/futex.h |  1 +
 io_uring/opdef.c |  2 +-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/io_uring/futex.c b/io_uring/futex.c
index 64f3bd51c84c6..57a17c6942219 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -144,6 +144,17 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	    !futex_validate_input(iof->futex_flags, iof->futex_mask))
 		return -EINVAL;
 
+	return 0;
+}
+
+int io_futex_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	int ret;
+
+	ret = io_futex_prep(req, sqe);
+	if (unlikely(ret))
+		return ret;
+
 	/* Mark as inflight, so file exit cancelation will find it */
 	io_req_track_inflight(req);
 	return 0;
diff --git a/io_uring/futex.h b/io_uring/futex.h
index d789fcf715e38..987db3f2c6d9a 100644
--- a/io_uring/futex.h
+++ b/io_uring/futex.h
@@ -3,6 +3,7 @@
 #include "cancel.h"
 
 int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_futex_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags);
 int io_futexv_wait(struct io_kiocb *req, unsigned int issue_flags);
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index a57c820567f77..0a3b684d72d80 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -466,7 +466,7 @@ const struct io_issue_def io_issue_defs[] = {
 	},
 	[IORING_OP_FUTEX_WAIT] = {
 #if defined(CONFIG_FUTEX)
-		.prep			= io_futex_prep,
+		.prep			= io_futex_wait_prep,
 		.issue			= io_futex_wait,
 #else
 		.prep			= io_eopnotsupp_prep,
-- 
2.53.0

[PATCH 6.18.y 2/2] io_uring/futex: only mark private futex waits as inflight

[Sasha Levin]

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 4d327bbd1cd2485783553b6b2b401aa475f90dd0 ]

Inflight tracking of futex wait requests exists to ensure that do_exit()
-> io_uring_files_cancel() cancels them before the mm goes away, as a
private futex wait depends on the mm private futex hash staying alive
for the duration of the request.

Shared futexes have no such dependency. A FLAGS_SHARED request always
resolves to either an inode based key or an mm-shared key, both of which
fail futex_key_is_private() and hence always hash into the global futex
hash, whose lifetime isn't tied to the mm.

Only mark vectored futex waits as inflight if the futex is private.

Cc: stable@vger.kernel.org
Fixes: 079afb081c42 ("io_uring/futex: mark wait requests as inflight")
Link: https://lore.kernel.org/io-uring/CANGjgdn=R_qyUdE=j9za+vkmqcxacbP-84OHXF4nZ4ho9qRyVg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[ kept 6.18's `struct futex_vector *futexv` declaration and changed `ifd->futexv[i].w.flags` to `futexv[i].w.flags` since `struct io_futexv_data` is absent, retaining the `iof->futexv_owned = 0;` init ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 io_uring/futex.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/io_uring/futex.c b/io_uring/futex.c
index 57a17c6942219..cccd1244c4b46 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -149,14 +149,16 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 int io_futex_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
 	int ret;
 
 	ret = io_futex_prep(req, sqe);
 	if (unlikely(ret))
 		return ret;
 
-	/* Mark as inflight, so file exit cancelation will find it */
-	io_req_track_inflight(req);
+	/* inflight tracking only needed for mm private hash */
+	if (!(iof->futex_flags & FLAGS_SHARED))
+		io_req_track_inflight(req);
 	return 0;
 }
 
@@ -179,6 +181,7 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
 	struct futex_vector *futexv;
+	unsigned int i;
 	int ret;
 
 	/* No flags or mask supported for waitv */
@@ -202,8 +205,14 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return ret;
 	}
 
-	/* Mark as inflight, so file exit cancelation will find it */
-	io_req_track_inflight(req);
+	/* inflight tracking only needed for mm private hash */
+	for (i = 0; i < iof->futex_nr; i++) {
+		if (!(futexv[i].w.flags & FLAGS_SHARED)) {
+			io_req_track_inflight(req);
+			break;
+		}
+	}
+
 	iof->futexv_owned = 0;
 	iof->futexv_unqueued = 0;
 	req->flags |= REQ_F_ASYNC_DATA;
-- 
2.53.0