linux-kernel - [PATCH AUTOSEL 6.1 9/9] safesetid: check size of policy writes

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Message-Id: <20250126145651.943149-9-sashal@kernel.org>
Date: Sun, 26 Jan 2025 09:56:51 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Leo Stone <leocstone@...il.com>,
	syzbot+4eb7a741b3216020043a@...kaller.appspotmail.com,
	Paul Moore <paul@...l-moore.com>,
	Sasha Levin <sashal@...nel.org>,
	mortonm@...omium.org,
	jmorris@...ei.org,
	serge@...lyn.com,
	linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 9/9] safesetid: check size of policy writes

From: Leo Stone <leocstone@...il.com>

[ Upstream commit f09ff307c7299392f1c88f763299e24bc99811c7 ]

syzbot attempts to write a buffer with a large size to a sysfs entry
with writes handled by handle_policy_update(), triggering a warning
in kmalloc.

Check the size specified for write buffers before allocating.

Reported-by: syzbot+4eb7a741b3216020043a@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4eb7a741b3216020043a
Signed-off-by: Leo Stone <leocstone@...il.com>
[PM: subject tweak]
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/safesetid/securityfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/safesetid/securityfs.c b/security/safesetid/securityfs.c
index 25310468bcddf..8e1ffd70b18ab 100644
--- a/security/safesetid/securityfs.c
+++ b/security/safesetid/securityfs.c
@@ -143,6 +143,9 @@ static ssize_t handle_policy_update(struct file *file,
 	char *buf, *p, *end;
 	int err;
 
+	if (len >= KMALLOC_MAX_SIZE)
+		return -EINVAL;
+
 	pol = kmalloc(sizeof(struct setid_ruleset), GFP_KERNEL);
 	if (!pol)
 		return -ENOMEM;
-- 
2.39.5