linux-kernel - [PATCH v2 next] ACPI: APEI: EINJ: prevent memory corruption in error_type

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Message-ID: <c71e7ba6-f127-4f49-acbf-20063dd26553@sabinyo.mountain>
Date: Wed, 25 Jun 2025 11:34:38 -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>,
	Dan Williams <dan.j.williams@...el.com>,
	Uwe Kleine-König <u.kleine-koenig@...libre.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Sudeep Holla <sudeep.holla@....com>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH v2 next] ACPI: APEI: EINJ: prevent memory corruption in
 error_type_set()

The "einj_buf" buffer is 32 chars.  Verify that "count" is not too large
for that.  Also leave the last character as a NUL terminator to ensure
the string is properly terminated.

Fixes: 0c6176e1e186 ("ACPI: APEI: EINJ: Enable the discovery of EINJv2 capabilities")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v2: I messed up the sizeof() calculation in the copy_from_user() and I put
    the parentheses in the wrong place in v1.

 drivers/acpi/apei/einj-core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
index d6d7e36e3647..2206cbbdccfa 100644
--- a/drivers/acpi/apei/einj-core.c
+++ b/drivers/acpi/apei/einj-core.c
@@ -826,8 +826,11 @@ static ssize_t error_type_set(struct file *file, const char __user *buf,
 	int rc;
 	u64 val;
 
+	if (count > sizeof(einj_buf))
+		return -EINVAL;
+
 	memset(einj_buf, 0, sizeof(einj_buf));
-	if (copy_from_user(einj_buf, buf, count))
+	if (copy_from_user(einj_buf, buf, min(count, sizeof(einj_buf) - 1)))
 		return -EFAULT;
 
 	if (strncmp(einj_buf, "V2_", 3) == 0) {
-- 
2.47.2