linux-kernel - [PATCH AUTOSEL 6.6 17/21] ima: process_measurement() needlessly takes inode_lock() on MAY

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Message-Id: <20250429235233.537828-17-sashal@kernel.org>
Date: Tue, 29 Apr 2025 19:52:29 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Frederick Lawler <fred@...udflare.com>,
	Roberto Sassu <roberto.sassu@...wei.com>,
	Mimi Zohar <zohar@...ux.ibm.com>,
	Sasha Levin <sashal@...nel.org>,
	dmitry.kasatkin@...il.com,
	paul@...l-moore.com,
	jmorris@...ei.org,
	serge@...lyn.com,
	linux-integrity@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 17/21] ima: process_measurement() needlessly takes inode_lock() on MAY_READ

From: Frederick Lawler <fred@...udflare.com>

[ Upstream commit 30d68cb0c37ebe2dc63aa1d46a28b9163e61caa2 ]

On IMA policy update, if a measure rule exists in the policy,
IMA_MEASURE is set for ima_policy_flags which makes the violation_check
variable always true. Coupled with a no-action on MAY_READ for a
FILE_CHECK call, we're always taking the inode_lock().

This becomes a performance problem for extremely heavy read-only workloads.
Therefore, prevent this only in the case there's no action to be taken.

Signed-off-by: Frederick Lawler <fred@...udflare.com>
Acked-by: Roberto Sassu <roberto.sassu@...wei.com>
Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/integrity/ima/ima_main.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 98308a2bdef6e..068edb0d79f73 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -235,7 +235,9 @@ static int process_measurement(struct file *file, const struct cred *cred,
 				&allowed_algos);
 	violation_check = ((func == FILE_CHECK || func == MMAP_CHECK ||
 			    func == MMAP_CHECK_REQPROT) &&
-			   (ima_policy_flag & IMA_MEASURE));
+			   (ima_policy_flag & IMA_MEASURE) &&
+			   ((action & IMA_MEASURE) ||
+			    (file->f_mode & FMODE_WRITE)));
 	if (!action && !violation_check)
 		return 0;
 
-- 
2.39.5