linux-kernel - [PATCH next] ACPI: APEI: EINJ: prevent memory corruption in error_type

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Message-ID: <ae6286cf-4d73-4b97-8c0f-0782a65b8f51@sabinyo.mountain>
Date: Wed, 25 Jun 2025 13:57:52 -0500
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Zaid Alali <zaidal@...amperecomputing.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	James Morse <james.morse@....com>, Tony Luck <tony.luck@...el.com>,
	Borislav Petkov <bp@...en8.de>, Ira Weiny <ira.weiny@...el.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Sudeep Holla <sudeep.holla@....com>,
	Jon Hunter <jonathanh@...dia.com>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH next] ACPI: APEI: EINJ: prevent memory corruption in
 error_type_set()

The "einj_buf" buffer is 32 chars.  If "count" is larger than that it
results in memory corruption.  Cap it at 31 so that we leave the last
character as a NUL terminator.  By the way, the highest reasonable value
for "count" is 24.

Fixes: 0c6176e1e186 ("ACPI: APEI: EINJ: Enable the discovery of EINJv2 capabilities")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v3: Style improvements.  Add a comment.
v2: I introduces a bug in v1 because I put parentheses in the wrong place.

 drivers/acpi/apei/einj-core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
index d6d7e36e3647..f5cfa6310f0e 100644
--- a/drivers/acpi/apei/einj-core.c
+++ b/drivers/acpi/apei/einj-core.c
@@ -826,6 +826,10 @@ static ssize_t error_type_set(struct file *file, const char __user *buf,
 	int rc;
 	u64 val;
 
+	/* Leave the last character for the NUL terminator */
+	if (count > sizeof(einj_buf) - 1)
+		return -EINVAL;
+
 	memset(einj_buf, 0, sizeof(einj_buf));
 	if (copy_from_user(einj_buf, buf, count))
 		return -EFAULT;
-- 
2.47.2