From fc68f42aa737dc15e7665a4101d4168aadb8e4c4 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 24 Jul 2021 15:25:54 -0700
Subject: [PATCH] ACPI: fix NULL pointer dereference
Git-commit: fc68f42aa737dc15e7665a4101d4168aadb8e4c4
Patch-mainline: v5.14-rc3
References: git-fixes

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@kernel.dk>
Tested-by: Daniel Scally <djrscally@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 include/acpi/acpi_bus.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -685,7 +685,8 @@ acpi_dev_get_first_match_dev(const char
 
 static inline void acpi_dev_put(struct acpi_device *adev)
 {
-	put_device(&adev->dev);
+	if (adev)
+		put_device(&adev->dev);
 }
 #else	/* CONFIG_ACPI */