linux-kernel - [PATCH AUTOSEL 5.4 2/4] efi: efivars: prevent double registration

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Message-Id: <20230301163007.1303162-2-sashal@kernel.org>
Date:   Wed,  1 Mar 2023 11:30:05 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-efi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 2/4] efi: efivars: prevent double registration

From: Johan Hovold <johan+linaro@...nel.org>

[ Upstream commit 0217a40d7ba6e71d7f3422fbe89b436e8ee7ece7 ]

Add the missing sanity check to efivars_register() so that it is no
longer possible to override an already registered set of efivar ops
(without first deregistering them).

This can help debug initialisation ordering issues where drivers have so
far unknowingly been relying on overriding the generic ops.

Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/firmware/efi/vars.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index a32d15b2928f7..87cbcbea40e90 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -1182,19 +1182,28 @@ int efivars_register(struct efivars *efivars,
 		     const struct efivar_operations *ops,
 		     struct kobject *kobject)
 {
+	int rv;
+
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
 
+	if (__efivars) {
+		pr_warn("efivars already registered\n");
+		rv = -EBUSY;
+		goto out;
+	}
+
 	efivars->ops = ops;
 	efivars->kobject = kobject;
 
 	__efivars = efivars;
 
 	pr_info("Registered efivars operations\n");
-
+	rv = 0;
+out:
 	up(&efivars_lock);
 
-	return 0;
+	return rv;
 }
 EXPORT_SYMBOL_GPL(efivars_register);
 
-- 
2.39.2