FAILED: patch "[PATCH] fuse: fix missing barrier when checking io-uring readiness" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] fuse: fix missing barrier when checking io-uring readiness" 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 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;

[PATCH 6.18.y 1/3] fuse: split off fuse_args and related definitions into a separate header

[Sasha Levin]

From: Miklos Szeredi <mszeredi@redhat.com>

[ Upstream commit 229f9b9b66ab5be9e015422cf30b97740cfbdc8d ]

This is going to be used by both layers (transport and filesystem)

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Stable-dep-of: edb310bc27f0 ("fuse: fix missing barrier when checking io-uring readiness")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/fuse/args.h   | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/fuse/fuse_i.h | 53 +--------------------------------------
 2 files changed, 66 insertions(+), 52 deletions(-)
 create mode 100644 fs/fuse/args.h

diff --git a/fs/fuse/args.h b/fs/fuse/args.h
new file mode 100644
index 0000000000000..12c94ece569fb
--- /dev/null
+++ b/fs/fuse/args.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _FS_FUSE_ARGS_H
+#define _FS_FUSE_ARGS_H
+
+#include <linux/types.h>
+
+struct fuse_mount;
+
+/** One input argument of a request */
+struct fuse_in_arg {
+	unsigned size;
+	const void *value;
+};
+
+/** One output argument of a request */
+struct fuse_arg {
+	unsigned size;
+	void *value;
+};
+
+struct fuse_args {
+	u64 nodeid;
+	u32 opcode;
+	u32 uid;
+	u32 gid;
+	u32 pid;
+	u8 in_numargs;
+	u8 out_numargs;
+	u8 ext_idx;
+	bool force:1;
+	bool noreply:1;
+	bool nocreds:1;
+	bool in_pages:1;
+	bool out_pages:1;
+	bool user_pages:1;
+	bool out_argvar:1;
+	bool page_zeroing:1;
+	bool page_replace:1;
+	bool may_block:1;
+	bool is_ext:1;
+	bool is_pinned:1;
+	bool invalidate_vmap:1;
+	bool abort_on_kill:1;
+	struct fuse_in_arg in_args[4];
+	struct fuse_arg out_args[2];
+	void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
+	/* Used for kvec iter backed by vmalloc address */
+	void *vmap_base;
+};
+
+/** FUSE folio descriptor */
+struct fuse_folio_desc {
+	unsigned int length;
+	unsigned int offset;
+};
+
+struct fuse_args_pages {
+	struct fuse_args args;
+	struct folio **folios;
+	struct fuse_folio_desc *descs;
+	unsigned int num_folios;
+};
+
+#endif /* _FS_FUSE_ARGS_H */
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index c288f28f6c6ea..7d26159af4059 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -13,6 +13,7 @@
 # define pr_fmt(fmt) "fuse: " fmt
 #endif
 
+#include "args.h"
 #include <linux/fuse.h>
 #include <linux/fs.h>
 #include <linux/mount.h>
@@ -296,58 +297,6 @@ struct fuse_file {
 	bool flock:1;
 };
 
-/** One input argument of a request */
-struct fuse_in_arg {
-	unsigned size;
-	const void *value;
-};
-
-/** One output argument of a request */
-struct fuse_arg {
-	unsigned size;
-	void *value;
-};
-
-/** FUSE folio descriptor */
-struct fuse_folio_desc {
-	unsigned int length;
-	unsigned int offset;
-};
-
-struct fuse_args {
-	uint64_t nodeid;
-	uint32_t opcode;
-	uint8_t in_numargs;
-	uint8_t out_numargs;
-	uint8_t ext_idx;
-	bool force:1;
-	bool noreply:1;
-	bool nocreds:1;
-	bool in_pages:1;
-	bool out_pages:1;
-	bool user_pages:1;
-	bool out_argvar:1;
-	bool page_zeroing:1;
-	bool page_replace:1;
-	bool may_block:1;
-	bool is_ext:1;
-	bool is_pinned:1;
-	bool invalidate_vmap:1;
-	bool abort_on_kill:1;
-	struct fuse_in_arg in_args[4];
-	struct fuse_arg out_args[2];
-	void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
-	/* Used for kvec iter backed by vmalloc address */
-	void *vmap_base;
-};
-
-struct fuse_args_pages {
-	struct fuse_args args;
-	struct folio **folios;
-	struct fuse_folio_desc *descs;
-	unsigned int num_folios;
-};
-
 struct fuse_release_args {
 	struct fuse_args args;
 	struct fuse_release_in inarg;
-- 
2.53.0

[PATCH 6.18.y 2/3] fuse: remove fm arg of args->end callback

[Sasha Levin]

From: Miklos Szeredi <mszeredi@redhat.com>

[ Upstream commit a697d95fcdbb3bbe25cdc29db5542ddcebb831c1 ]

Only used by FUSE_INIT and CUSE_INIT, these can store the relevant pointer
in their structs derived from fuse_args.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Stable-dep-of: edb310bc27f0 ("fuse: fix missing barrier when checking io-uring readiness")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/fuse/args.h  |  2 +-
 fs/fuse/cuse.c  |  7 ++++---
 fs/fuse/dev.c   |  7 +++----
 fs/fuse/file.c  | 22 +++++++++-------------
 fs/fuse/inode.c | 10 ++++++----
 5 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/fs/fuse/args.h b/fs/fuse/args.h
index 12c94ece569fb..ecfe51a192af0 100644
--- a/fs/fuse/args.h
+++ b/fs/fuse/args.h
@@ -44,7 +44,7 @@ struct fuse_args {
 	bool abort_on_kill:1;
 	struct fuse_in_arg in_args[4];
 	struct fuse_arg out_args[2];
-	void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
+	void (*end)(struct fuse_args *args, int error);
 	/* Used for kvec iter backed by vmalloc address */
 	void *vmap_base;
 };
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 2bb98bf81b079..e43d12f69d655 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -306,6 +306,7 @@ struct cuse_init_args {
 	struct cuse_init_out out;
 	struct folio *folio;
 	struct fuse_folio_desc desc;
+	struct fuse_conn *fc;
 };
 
 /**
@@ -319,11 +320,10 @@ struct cuse_init_args {
  * required data structures for it.  Please read the comment at the
  * top of this file for high level overview.
  */
-static void cuse_process_init_reply(struct fuse_mount *fm,
-				    struct fuse_args *args, int error)
+static void cuse_process_init_reply(struct fuse_args *args, int error)
 {
-	struct fuse_conn *fc = fm->fc;
 	struct cuse_init_args *ia = container_of(args, typeof(*ia), ap.args);
+	struct fuse_conn *fc = ia->fc;
 	struct fuse_args_pages *ap = &ia->ap;
 	struct cuse_conn *cc = fc_to_cc(fc), *pos;
 	struct cuse_init_out *arg = &ia->out;
@@ -468,6 +468,7 @@ static int cuse_send_init(struct cuse_conn *cc)
 	ap->descs = &ia->desc;
 	ia->folio = folio;
 	ia->desc.length = ap->args.out_args[1].size;
+	ia->fc = &cc->fc;
 	ap->args.end = cuse_process_init_reply;
 
 	rc = fuse_simple_background(fm, &ap->args, GFP_KERNEL);
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 77c3982bca3d7..8a38a263295fe 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -512,7 +512,7 @@ void fuse_request_end(struct fuse_req *req)
 	}
 
 	if (test_bit(FR_ASYNC, &req->flags))
-		req->args->end(fm, req->args, req->out.h.error);
+		req->args->end(req->args, req->out.h.error);
 put_request:
 	fuse_put_request(req);
 }
@@ -1859,8 +1859,7 @@ struct fuse_retrieve_args {
 	struct fuse_notify_retrieve_in inarg;
 };
 
-static void fuse_retrieve_end(struct fuse_mount *fm, struct fuse_args *args,
-			      int error)
+static void fuse_retrieve_end(struct fuse_args *args, int error)
 {
 	struct fuse_retrieve_args *ra =
 		container_of(args, typeof(*ra), ap.args);
@@ -1955,7 +1954,7 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
 
 	err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
 	if (err)
-		fuse_retrieve_end(fm, args, err);
+		fuse_retrieve_end(args, err);
 
 	return err;
 }
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 585dd90361b65..f3b4d6ae0858a 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -91,8 +91,7 @@ static struct fuse_file *fuse_file_get(struct fuse_file *ff)
 	return ff;
 }
 
-static void fuse_release_end(struct fuse_mount *fm, struct fuse_args *args,
-			     int error)
+static void fuse_release_end(struct fuse_args *args, int error)
 {
 	struct fuse_release_args *ra = container_of(args, typeof(*ra), args);
 
@@ -112,15 +111,15 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
 		if (!args) {
 			/* Do nothing when server does not implement 'opendir' */
 		} else if (args->opcode == FUSE_RELEASE && ff->fm->fc->no_open) {
-			fuse_release_end(ff->fm, args, 0);
+			fuse_release_end(args, 0);
 		} else if (sync) {
 			fuse_simple_request(ff->fm, args);
-			fuse_release_end(ff->fm, args, 0);
+			fuse_release_end(args, 0);
 		} else {
 			args->end = fuse_release_end;
 			if (fuse_simple_background(ff->fm, args,
 						   GFP_KERNEL | __GFP_NOFAIL))
-				fuse_release_end(ff->fm, args, -ENOTCONN);
+				fuse_release_end(args, -ENOTCONN);
 		}
 		kfree(ff);
 	}
@@ -709,8 +708,7 @@ static void fuse_io_free(struct fuse_io_args *ia)
 	kfree(ia);
 }
 
-static void fuse_aio_complete_req(struct fuse_mount *fm, struct fuse_args *args,
-				  int err)
+static void fuse_aio_complete_req(struct fuse_args *args, int err)
 {
 	struct fuse_io_args *ia = container_of(args, typeof(*ia), ap.args);
 	struct fuse_io_priv *io = ia->io;
@@ -758,7 +756,7 @@ static ssize_t fuse_async_req_send(struct fuse_mount *fm,
 	ia->ap.args.may_block = io->should_dirty;
 	err = fuse_simple_background(fm, &ia->ap.args, GFP_KERNEL);
 	if (err)
-		fuse_aio_complete_req(fm, &ia->ap.args, err);
+		fuse_aio_complete_req(&ia->ap.args, err);
 
 	return num_bytes;
 }
@@ -881,8 +879,7 @@ static int fuse_iomap_read_folio_range(const struct iomap_iter *iter,
 	return fuse_do_readfolio(file, folio, off, len);
 }
 
-static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
-			       int err)
+static void fuse_readpages_end(struct fuse_args *args, int err)
 {
 	int i;
 	struct fuse_io_args *ia = container_of(args, typeof(*ia), ap.args);
@@ -947,7 +944,7 @@ static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file,
 		res = fuse_simple_request(fm, &ap->args);
 		err = res < 0 ? res : 0;
 	}
-	fuse_readpages_end(fm, &ap->args, err);
+	fuse_readpages_end(&ap->args, err);
 }
 
 static void fuse_readahead(struct readahead_control *rac)
@@ -1950,8 +1947,7 @@ __acquires(fi->lock)
 	}
 }
 
-static void fuse_writepage_end(struct fuse_mount *fm, struct fuse_args *args,
-			       int error)
+static void fuse_writepage_end(struct fuse_args *args, int error)
 {
 	struct fuse_writepage_args *wpa =
 		container_of(args, typeof(*wpa), ia.ap.args);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e9ed693fc7b37..ae520c7388218 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1311,13 +1311,14 @@ struct fuse_init_args {
 	struct fuse_args args;
 	struct fuse_init_in in;
 	struct fuse_init_out out;
+	struct fuse_mount *fm;
 };
 
-static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
-			       int error)
+static void process_init_reply(struct fuse_args *args, int error)
 {
-	struct fuse_conn *fc = fm->fc;
 	struct fuse_init_args *ia = container_of(args, typeof(*ia), args);
+	struct fuse_mount *fm = ia->fm;
+	struct fuse_conn *fc = fm->fc;
 	struct fuse_init_out *arg = &ia->out;
 	bool ok = true;
 
@@ -1486,6 +1487,7 @@ static struct fuse_init_args *fuse_new_init(struct fuse_mount *fm)
 
 	ia = kzalloc(sizeof(*ia), GFP_KERNEL | __GFP_NOFAIL);
 
+	ia->fm = fm;
 	ia->in.major = FUSE_KERNEL_VERSION;
 	ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
 	ia->in.max_readahead = fm->sb->s_bdi->ra_pages * PAGE_SIZE;
@@ -1559,7 +1561,7 @@ int fuse_send_init(struct fuse_mount *fm)
 		if (!err)
 			return 0;
 	}
-	process_init_reply(fm, &ia->args, err);
+	process_init_reply(&ia->args, err);
 	if (fm->fc->conn_error)
 		return -ENOTCONN;
 	return 0;
-- 
2.53.0

[PATCH 6.18.y 3/3] fuse: fix missing barrier when checking io-uring readiness

[Sasha Levin]

From: Joanne Koong <joannelkoong@gmail.com>

[ Upstream commit edb310bc27f0ad83e7fd558a3caf1a94ca511654 ]

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>
[ renamed `fch`/`struct fuse_chan` to `fc`/`struct fuse_conn` and `fuse_chan_set_initialized()` to `fuse_set_initialized()` in the comment ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/fuse/dev.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 8a38a263295fe..33e01d67e5151 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -172,7 +172,13 @@ void fuse_set_initialized(struct fuse_conn *fc)
 
 static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
 {
-	return !fc->initialized || (for_background && fc->blocked) ||
+	if (!fc->initialized)
+		return true;
+
+	/* Pairs with smp_wmb() in fuse_set_initialized() */
+	smp_rmb();
+
+	return (for_background && fc->blocked) ||
 	       (fc->io_uring && fc->connected && !fuse_uring_ready(fc));
 }
 
@@ -212,8 +218,6 @@ static struct fuse_req *fuse_get_req(struct mnt_idmap *idmap,
 				(TASK_KILLABLE | TASK_FREEZABLE)))
 			goto out;
 	}
-	/* Matches smp_wmb() in fuse_set_initialized() */
-	smp_rmb();
 
 	err = -ENOTCONN;
 	if (!fc->connected)
-- 
2.53.0