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From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Mike Snitzer <snitzer@kernel.org>,
        Joern Engel <joern@lazybastard.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Pavel Machek <pavel@ucw.cz>, dm-devel@redhat.com,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-mtd@lists.infradead.org, linux-pm@vger.kernel.org
Subject: [PATCH 21/24] PM: hibernate: don't use early_lookup_bdev in resume_store
Date:   Tue, 23 May 2023 09:45:32 +0200
Message-Id: <20230523074535.249802-22-hch@lst.de>
In-Reply-To: <20230523074535.249802-1-hch@lst.de>
References: <20230523074535.249802-1-hch@lst.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

resume_store is a sysfs attribute written during normal kernel runtime,
and it should not use the early_lookup_bdev API that bypasses all normal
path based permission checking, and might cause problems with certain
container environments renaming devices.

Switch to lookup_bdev, which does a normal path lookup instead, and fall
back to trying to parse a numeric dev_t just like early_lookup_bdev did.

Note that this strictly speaking changes the kernel ABI as the PARTUUID=
and PARTLABEL= style syntax is now not available during a running
systems.  They never were intended for that, but this breaks things
we'll have to figure out a way to make them available again.  But if
avoidable in any way I'd rather avoid that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 421a5fa1a6cf ("PM / hibernate: use name_to_dev_t to parse resume")
---
 kernel/power/hibernate.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index c52dedb9f7c8e8..7ae95ec72f9902 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1178,7 +1178,23 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (!name)
 		return -ENOMEM;
 
-	error = early_lookup_bdev(name, &dev);
+	error = lookup_bdev(name, &dev);
+	if (error) {
+		unsigned maj, min, offset;
+		char *p, dummy;
+
+		if (sscanf(name, "%u:%u%c", &maj, &min, &dummy) == 2 ||
+		    sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset,
+				&dummy) == 3) {
+			dev = MKDEV(maj, min);
+			if (maj != MAJOR(dev) || min != MINOR(dev))
+				error = -EINVAL;
+		} else {
+			dev = new_decode_dev(simple_strtoul(name, &p, 16));
+			if (*p)
+				error = -EINVAL;
+		}
+	}
 	kfree(name);
 	if (error)
 		return error;
-- 
2.39.2