linux-kernel - [PATCH AUTOSEL 6.12 11/26] ACPI: bus: Bail out if acpi

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Message-Id: <20250530124012.2575409-11-sashal@kernel.org>
Date: Fri, 30 May 2025 08:39:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: patches@...ts.linux.dev,
	stable@...r.kernel.org
Cc: Armin Wolf <W_Armin@....de>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Sasha Levin <sashal@...nel.org>,
	rjw@...ysocki.net,
	lenb@...nel.org,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 6.12 11/26] ACPI: bus: Bail out if acpi_kobj registration fails

From: Armin Wolf <W_Armin@....de>

[ Upstream commit 94a370fc8def6038dbc02199db9584b0b3690f1a ]

The ACPI sysfs code will fail to initialize if acpi_kobj is NULL,
together with some ACPI drivers.

Follow the other firmware subsystems and bail out if the kobject
cannot be registered.

Signed-off-by: Armin Wolf <W_Armin@....de>
Link: https://patch.msgid.link/20250518185111.3560-2-W_Armin@gmx.de
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---

**YES** This commit should be backported to stable kernel trees. Here's
my extensive analysis: ## Code Change Analysis The commit changes the
behavior in `acpi_init()` when `kobject_create_and_add("acpi",
firmware_kobj)` fails: **Before:** - If `acpi_kobj` creation fails, only
prints a debug message and continues execution - The function proceeds
to initialize ACPI subsystems with a NULL `acpi_kobj` - This leads to
potential crashes/failures in other ACPI components **After:** - If
`acpi_kobj` creation fails, prints an error message and returns
`-ENOMEM` - Prevents initialization of ACPI subsystems with a NULL
`acpi_kobj` - Follows proper error handling patterns ## Evidence from
Kernel Code Investigation From examining the kernel repository, I found
multiple critical usages of `acpi_kobj` that would fail catastrophically
if it's NULL: 1. **drivers/acpi/sysfs.c:514**:
`kobject_create_and_add("tables", acpi_kobj)` - NULL parent causes
undefined behavior 2. **drivers/acpi/sysfs.c:924**:
`sysfs_create_group(acpi_kobj, &interrupt_stats_attr_group)` - NULL
kobject crashes 3. **drivers/acpi/platform_profile.c**: Multiple
`sysfs_notify(acpi_kobj, ...)` calls that would crash with NULL 4.
**drivers/acpi/platform_profile.c**: `sysfs_create_group(acpi_kobj,
&platform_profile_group)` would fail ## Backport Criteria Assessment ✅
**Fixes a real bug**: Yes - prevents crashes when kobject creation fails
✅ **Small and contained**: Yes - only 4 lines changed in one function ✅
**Clear side effects**: Yes - prevents ACPI initialization on memory
allocation failure ✅ **No architectural changes**: Yes - just proper
error handling ✅ **Critical subsystem**: Yes - ACPI is core kernel
infrastructure ✅ **Minimal regression risk**: Yes - only affects rare
failure path ✅ **Follows stable rules**: Yes - important bugfix with
minimal risk ## Comparison with Historical Examples This commit closely
matches **Similar Commit #1** (Status: YES) which also: - Fixed error
handling in ACPI initialization code - Added proper cleanup/error
handling when kobject operations fail - Was considered suitable for
backporting The commit differs significantly from the "NO" examples
which were: - Code cleanup/style changes (Similar Commits #2, #3, #4) -
Refactoring without fixing actual bugs (Similar Commit #4) ## Risk
Assessment **Low Risk**: The change only affects the extremely rare case
where `kobject_create_and_add()` fails due to memory allocation failure.
In such cases: - **Current behavior**: System continues with broken
ACPI, leading to crashes - **New behavior**: ACPI initialization fails
cleanly, system may still boot without ACPI ## Conclusion This is a
critical bug fix that prevents crashes in ACPI subsystems when memory
allocation fails during boot. It transforms undefined behavior/crashes
into clean failure handling, making it an ideal candidate for stable
backporting.

 drivers/acpi/bus.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 16917dc3ad604..6234055d25984 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -1444,8 +1444,10 @@ static int __init acpi_init(void)
 	}

 	acpi_kobj = kobject_create_and_add("acpi", firmware_kobj);
-	if (!acpi_kobj)
-		pr_debug("%s: kset create error\n", __func__);
+	if (!acpi_kobj) {
+		pr_err("Failed to register kobject\n");
+		return -ENOMEM;
+	}

 	init_prmt();
 	acpi_init_pcc();
-- 
2.39.5