linux-kernel - [PATCH] ima: kexec: Add RCU read lock protection for ima

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Message-Id: <20241104-ima_rcu-v1-1-5157460c5907@debian.org>
Date: Mon, 04 Nov 2024 02:47:16 -0800
From: Breno Leitao <leitao@...ian.org>
To: Mimi Zohar <zohar@...ux.ibm.com>, 
 Roberto Sassu <roberto.sassu@...wei.com>, 
 Dmitry Kasatkin <dmitry.kasatkin@...il.com>, 
 Eric Snowberg <eric.snowberg@...cle.com>, Paul Moore <paul@...l-moore.com>, 
 James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, 
 "Eric W. Biederman" <ebiederm@...ssion.com>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc: Mimi Zohar <zohar@...ux.vnet.ibm.com>, linux-integrity@...r.kernel.org, 
 linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, 
 noodles@...th.li, Breno Leitao <leitao@...ian.org>
Subject: [PATCH] ima: kexec: Add RCU read lock protection for
 ima_measurements list traversal

Fix a potential RCU issue where ima_measurements list is traversed using
list_for_each_entry_rcu() without proper RCU read lock protection. This
caused warnings when CONFIG_PROVE_RCU was enabled:

  security/integrity/ima/ima_kexec.c:40 RCU-list traversed in non-reader section!!

Add rcu_read_lock() before iterating over ima_measurements list to ensure
proper RCU synchronization, consistent with other RCU list traversals in
the codebase.

Signed-off-by: Breno Leitao <leitao@...ian.org>
Fixes: 7b8589cc29e7 ("ima: on soft reboot, save the measurement list")
---
 security/integrity/ima/ima_kexec.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 52e00332defed39774c9e23e045f1377cfa30d0c..3b17ddb91d35ac806aedd2ee970ff365675dac0b 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -37,6 +37,7 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,

 	memset(&khdr, 0, sizeof(khdr));
 	khdr.version = 1;
+	rcu_read_lock();
 	list_for_each_entry_rcu(qe, &ima_measurements, later) {
 		if (file.count < file.size) {
 			khdr.count++;
@@ -46,6 +47,7 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 			break;
 		}
 	}
+	rcu_read_unlock();

 	if (ret < 0)
 		goto out;

---
base-commit: f488649e40f8900d23b86afeab7d4b78c063d5d1
change-id: 20241104-ima_rcu-ee83da87d050

Best regards,
-- 
Breno Leitao <leitao@...ian.org>