linux-kernel - [PATCH 01/21] liveupdate: luo_flb: Prevent retrieve() after finish()

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Message-ID: <20251126193608.2678510-2-dmatlack@google.com>
Date: Wed, 26 Nov 2025 19:35:48 +0000
From: David Matlack <dmatlack@...gle.com>
To: Alex Williamson <alex@...zbot.org>
Cc: Adithya Jayachandran <ajayachandra@...dia.com>, Alex Mastro <amastro@...com>, 
	Alistair Popple <apopple@...dia.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Chris Li <chrisl@...nel.org>, 
	David Matlack <dmatlack@...gle.com>, David Rientjes <rientjes@...gle.com>, 
	Jacob Pan <jacob.pan@...ux.microsoft.com>, Jason Gunthorpe <jgg@...dia.com>, 
	Jason Gunthorpe <jgg@...pe.ca>, Josh Hilke <jrhilke@...gle.com>, Kevin Tian <kevin.tian@...el.com>, 
	kvm@...r.kernel.org, Leon Romanovsky <leonro@...dia.com>, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-pci@...r.kernel.org, 
	Lukas Wunner <lukas@...ner.de>, Mike Rapoport <rppt@...nel.org>, Parav Pandit <parav@...dia.com>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Philipp Stanner <pstanner@...hat.com>, 
	Pratyush Yadav <pratyush@...nel.org>, Saeed Mahameed <saeedm@...dia.com>, 
	Samiullah Khawaja <skhawaja@...gle.com>, Shuah Khan <shuah@...nel.org>, 
	Tomita Moeko <tomitamoeko@...il.com>, Vipin Sharma <vipinsh@...gle.com>, William Tu <witu@...dia.com>, 
	Yi Liu <yi.l.liu@...el.com>, Yunxiang Li <Yunxiang.Li@....com>, 
	Zhu Yanjun <yanjun.zhu@...ux.dev>
Subject: [PATCH 01/21] liveupdate: luo_flb: Prevent retrieve() after finish()

Prevent an incoming FLB from being retrieved after its finish() callback
has been run. An incoming FLB should only retrieved once, and once its
finish() callback has run the data has been freed and cannot be (and
should not be) retrieved again.

Fixes: e8c57e582167 ("liveupdate: luo_flb: Introduce File-Lifecycle-Bound global state")
Signed-off-by: David Matlack <dmatlack@...gle.com>
---
 include/linux/liveupdate.h  | 3 +++
 kernel/liveupdate/luo_flb.c | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index ed81e7b31a9f..b913d63eab5f 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -165,12 +165,15 @@ struct liveupdate_flb_ops {
  * @obj:   The live kernel object returned by .preserve() or .retrieve().
  * @lock:  A mutex that protects all fields within this structure, providing
  *         the synchronization service for the FLB's ops.
+ * @finished: True once the FLB's finish() callback has run, to prevent an FLB
+ *            from being retrieve()'d again after finish() (incoming only).
  */
 struct luo_flb_private_state {
 	long count;
 	u64 data;
 	void *obj;
 	struct mutex lock;
+	bool finished;
 };
 
 /*
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index e80ac5b575ec..072796fb75cb 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -155,6 +155,9 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
 
 	guard(mutex)(&private->incoming.lock);
 
+	if (private->incoming.finished)
+		return -ENODATA;
+
 	if (private->incoming.obj)
 		return 0;
 
@@ -213,6 +216,7 @@ static void luo_flb_file_finish_one(struct liveupdate_flb *flb)
 
 			private->incoming.data = 0;
 			private->incoming.obj = NULL;
+			private->incoming.finished = true;
 		}
 	}
 }
-- 
2.52.0.487.g5c8c507ade-goog