linux-kernel - [PATCH] gsmi: fix null-deref in gsmi_get

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Message-Id: <20230118010212.1268474-1-khazhy@google.com>
Date:   Tue, 17 Jan 2023 17:02:12 -0800
From:   Khazhismel Kumykov <khazhy@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        Evan Green <evgreen@...omium.org>,
        Khazhismel Kumykov <khazhy@...gle.com>
Subject: [PATCH] gsmi: fix null-deref in gsmi_get_variable

We can get EFI variables without fetching the attribute, so we must
allow for that in gsmi.

commit 859748255b43 ("efi: pstore: Omit efivars caching EFI varstore
access layer") added a new get_variable call with attr=NULL, which
triggers panic in gsmi.

Fixes: 74c5b31c6618 ("driver: Google EFI SMI")
Signed-off-by: Khazhismel Kumykov <khazhy@...gle.com>
---
 drivers/firmware/google/gsmi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c
index 4e2575dfeb90..871bedf533a8 100644
--- a/drivers/firmware/google/gsmi.c
+++ b/drivers/firmware/google/gsmi.c
@@ -361,9 +361,10 @@ static efi_status_t gsmi_get_variable(efi_char16_t *name,
 		memcpy(data, gsmi_dev.data_buf->start, *data_size);
 
 		/* All variables are have the following attributes */
-		*attr = EFI_VARIABLE_NON_VOLATILE |
-			EFI_VARIABLE_BOOTSERVICE_ACCESS |
-			EFI_VARIABLE_RUNTIME_ACCESS;
+		if (attr)
+			*attr = EFI_VARIABLE_NON_VOLATILE |
+				EFI_VARIABLE_BOOTSERVICE_ACCESS |
+				EFI_VARIABLE_RUNTIME_ACCESS;
 	}
 
 	spin_unlock_irqrestore(&gsmi_dev.lock, flags);
-- 
2.39.0.314.g84b9a713c41-goog