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* FAILED: patch "[PATCH] fuse: fix missing barrier when checking io-uring readiness" failed to apply to 6.18-stable tree
@ 2026-08-31 12:22 gregkh
  2026-08-31 16:42 ` [PATCH 6.18.y 1/3] fuse: split off fuse_args and related definitions into a separate header Sasha Levin
  0 siblings, 1 reply; 5+ messages in thread
From: gregkh @ 2026-08-31 12:22 UTC (permalink / raw)
  To: joannelkoong, bernd, mszeredi; +Cc: stable


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 edb310bc27f0ad83e7fd558a3caf1a94ca511654
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026083142-tingly-scarecrow-e145@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From edb310bc27f0ad83e7fd558a3caf1a94ca511654 Mon Sep 17 00:00:00 2001
From: Joanne Koong <joannelkoong@gmail.com>
Date: Thu, 16 Jul 2026 11:31:42 -0700
Subject: [PATCH] fuse: fix missing barrier when checking io-uring readiness

fuse_block_alloc() reads fch->initialized and then fch->io_uring.
fch->io_uring is set before fch->initialized, ordered by the smp_wmb()
in fuse_chan_set_intialized(), but fuse_block_alloc() has no matching
read barrier between the two loads.

This may lead a CPU to observe fch->initialized=1 but fch->io_uring=0,
and skip the check that blocks request allocation until the io-uring
queues are ready. This can reintroduce the lock-order inversion deadlock
that commit 3393ff964e0f prevents.

Add an smp_rmb() barrier to pair with the smp_wmb() in
fuse_chan_set_initialized() to prevent this.

Fixes: 3393ff964e0f ("fuse: block request allocation until io-uring init is complete")
Cc: stable@vger.kernel.org
Reviewed-by: Bernd Schubert <bernd@bsbernd.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 7e81dea4f1c7..a27ea64d763a 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -85,7 +85,13 @@ void fuse_chan_set_initialized(struct fuse_chan *fch, struct fuse_chan_param *pa
 
 static bool fuse_block_alloc(struct fuse_chan *fch, bool for_background)
 {
-	return !fch->initialized || (for_background && fch->blocked) ||
+	if (!fch->initialized)
+		return true;
+
+	/* Pairs with smp_wmb() in fuse_chan_set_initialized() */
+	smp_rmb();
+
+	return (for_background && fch->blocked) ||
 	       (fch->io_uring && fch->connected && !fuse_uring_ready(fch));
 }
 
@@ -120,9 +126,6 @@ static struct fuse_req *fuse_get_req(struct fuse_chan *fch, bool for_background)
 			goto out;
 	}
 
-	/* Matches smp_wmb() in fuse_chan_set_initialized() */
-	smp_rmb();
-
 	err = -ENOTCONN;
 	if (!fch->connected)
 		goto out;


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* FAILED: patch "[PATCH] fuse: fix race between interrupt and resend" failed to apply to 6.18-stable tree
@ 2026-08-31 12:22 gregkh
  2026-08-31 16:43 ` [PATCH 6.18.y 1/3] fuse: split off fuse_args and related definitions into a separate header Sasha Levin
  0 siblings, 1 reply; 5+ messages in thread
From: gregkh @ 2026-08-31 12:22 UTC (permalink / raw)
  To: mszeredi; +Cc: stable


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 ed9c881f3b498383f73c42712b359419da42a7b0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026083132-jaybird-willed-acf3@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From ed9c881f3b498383f73c42712b359419da42a7b0 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 9 Jul 2026 08:37:05 +0200
Subject: [PATCH] fuse: fix race between interrupt and resend

After commit f8fce75fedf7 ("fuse: clear intr_entry in fuse_resend and
fuse_remove_pending_req") the WARN_ON(!list_empty(&req->intr_entry)) in
fuse_request_free() still triggers due to the following race:

In request_wait_answer()
  if (test_bit(FR_SENT, &req->flags)) -> returns true

In fuse_chan_resend()
  clear_bit(FR_SENT, &req->flags)

In request_wait_answer()
  queue_interrupt(req)

Fix by:

 - move clearing FR_SENT inside fpq->lock

 - move setting FR_PENDING inside fiq->lock

 - recheck FR_SENT after acquiring fiq->lock in fuse_dev_queue_interrupt()

Reported-by: zdi-disclosures@trendmicro.com
Fixes: f8fce75fedf7 ("fuse: clear intr_entry in fuse_resend and fuse_remove_pending_req")
Cc: stable@vger.kernel.org # 6.9
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 5763a7cd3b37..7e81dea4f1c7 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -240,7 +240,8 @@ void fuse_dev_queue_forget(struct fuse_iqueue *fiq,
 void fuse_dev_queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
 {
 	spin_lock(&fiq->lock);
-	if (list_empty(&req->intr_entry)) {
+	/* Repeat FR_SENT test after obtaining the lock to prevent race with fuse_resend() */
+	if (list_empty(&req->intr_entry) && test_bit(FR_SENT, &req->flags)) {
 		list_add_tail(&req->intr_entry, &fiq->interrupts);
 		/*
 		 * Pairs with smp_mb() implied by test_and_set_bit()
@@ -1760,7 +1761,7 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
 void fuse_chan_resend(struct fuse_chan *fch)
 {
 	struct fuse_dev *fud;
-	struct fuse_req *req, *next;
+	struct fuse_req *req;
 	struct fuse_iqueue *fiq = &fch->iq;
 	LIST_HEAD(to_queue);
 	unsigned int i;
@@ -1775,24 +1776,20 @@ void fuse_chan_resend(struct fuse_chan *fch)
 		struct fuse_pqueue *fpq = &fud->pq;
 
 		spin_lock(&fpq->lock);
-		for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
-			list_splice_tail_init(&fpq->processing[i], &to_queue);
+		for (i = 0; i < FUSE_PQ_HASH_SIZE; i++) {
+			struct list_head *this_queue = &fpq->processing[i];
+
+			list_for_each_entry(req, this_queue, list)
+				clear_bit(FR_SENT, &req->flags);
+			list_splice_tail_init(this_queue, &to_queue);
+		}
 		spin_unlock(&fpq->lock);
 	}
 	spin_unlock(&fch->lock);
 
-	list_for_each_entry_safe(req, next, &to_queue, list) {
-		set_bit(FR_PENDING, &req->flags);
-		clear_bit(FR_SENT, &req->flags);
-		/* mark the request as resend request */
-		req->in.h.unique |= FUSE_UNIQUE_RESEND;
-	}
-
 	spin_lock(&fiq->lock);
 	if (!fiq->connected) {
 		spin_unlock(&fiq->lock);
-		list_for_each_entry(req, &to_queue, list)
-			clear_bit(FR_PENDING, &req->flags);
 		fuse_dev_end_requests(&to_queue);
 		return;
 	}
@@ -1801,6 +1798,10 @@ void fuse_chan_resend(struct fuse_chan *fch)
 	 * intr_entry on fiq->interrupts after the request is re-queued.
 	 */
 	list_for_each_entry(req, &to_queue, list) {
+		set_bit(FR_PENDING, &req->flags);
+		/* mark the request as resend request */
+		req->in.h.unique |= FUSE_UNIQUE_RESEND;
+
 		if (test_bit(FR_INTERRUPTED, &req->flags))
 			list_del_init(&req->intr_entry);
 	}


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-08-31 16:43 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2026-08-31 12:22 FAILED: patch "[PATCH] fuse: fix missing barrier when checking io-uring readiness" failed to apply to 6.18-stable tree gregkh
2026-08-31 16:42 ` [PATCH 6.18.y 1/3] fuse: split off fuse_args and related definitions into a separate header Sasha Levin
2026-08-31 16:42   ` [PATCH 6.18.y 2/3] fuse: remove fm arg of args->end callback Sasha Levin
2026-08-31 16:42   ` [PATCH 6.18.y 3/3] fuse: fix missing barrier when checking io-uring readiness Sasha Levin
  -- strict thread matches above, loose matches on Subject: below --
2026-08-31 12:22 FAILED: patch "[PATCH] fuse: fix race between interrupt and resend" failed to apply to 6.18-stable tree gregkh
2026-08-31 16:43 ` [PATCH 6.18.y 1/3] fuse: split off fuse_args and related definitions into a separate header Sasha Levin
2026-08-31 16:43   ` [PATCH 6.18.y 2/3] fuse: remove fm arg of args->end callback Sasha Levin

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