linux-kernel - [PATCH AUTOSEL 5.4 9/9] ACPI: fix NULL pointer dereference

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Date:   Tue, 27 Jul 2021 09:20:01 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Daniel Scally <djrscally@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Sasha Levin <sashal@...nel.org>, linux-acpi@...r.kernel.org,
        devel@...ica.org
Subject: [PATCH AUTOSEL 5.4 9/9] ACPI: fix NULL pointer dereference

From: Linus Torvalds <torvalds@...ux-foundation.org>

[ Upstream commit fc68f42aa737dc15e7665a4101d4168aadb8e4c4 ]

Commit 71f642833284 ("ACPI: utils: Fix reference counting in
for_each_acpi_dev_match()") started doing "acpi_dev_put()" on a pointer
that was possibly NULL.  That fails miserably, because that helper
inline function is not set up to handle that case.

Just make acpi_dev_put() silently accept a NULL pointer, rather than
calling down to put_device() with an invalid offset off that NULL
pointer.

Link: https://lore.kernel.org/lkml/a607c149-6bf6-0fd0-0e31-100378504da2@kernel.dk/
Reported-and-tested-by: Jens Axboe <axboe@...nel.dk>
Tested-by: Daniel Scally <djrscally@...il.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/acpi/acpi_bus.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 4d67a67964fa..1e5ae3b01eb2 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -681,7 +681,8 @@ acpi_dev_get_first_match_dev(const char *hid, const char *uid, s64 hrv);
 
 static inline void acpi_dev_put(struct acpi_device *adev)
 {
-	put_device(&adev->dev);
+	if (adev)
+		put_device(&adev->dev);
 }
 #else	/* CONFIG_ACPI */
 
-- 
2.30.2