Re: [PATCH 2/2] ima: don't measure/appraise files on configfs
From: Mimi Zohar <zohar@linux.ibm.com>
Date: 2026-08-19 18:40:01
Also in:
linux-integrity, lkml
On Tue, 2026-08-18 at 14:35 -0500, Frederick Lawler wrote:
When IMA appraises/measures a file configfs, it has an opportunity to hold onto the ima_iint_mutex while another file from a different file system is attempting to appraise/measure. This may cause a cyclical lock dependency.
The locking description is off a bit. Suggested patch desciption from AI: IMA measurement of a configfs file causes process_measurement() to hold iint-
mutex while performing a kernel_read() to hash it, which re-enters configfs's
own file locking (buffer->mutex, frag_sem). Separately, opening any file with O_TRUNC now causes ima_file_truncate() to take iint->mutex to reset the cached action flags, while sb_writers is already held for that mount. When a configfs-backed nvmet namespace is involved, these two independent lock chains combine into a cycle: iint->mutex -> configfs locks -> subsys->lock -> sb_writers -> iint->mutex Add configfs to the builtin don't measure/appraise rules, similarly to other pseudo file systems, so IMA never takes iint->mutex for configfs file in the first place.
Add configfs to the default don't measure/appraise lists, similarly to other pseudo file systems. Reported-by: syzbot+448c2e24b1ceff13ed2a@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/6a77c7cd.b50370da.49fe0.0031.GAE@google.com/ (local) Suggested-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Frederick Lawler <redacted>
Sashiko is now enabled for the linux-integrity mailing list - https://sashiko.dev/#/?list=org.kernel.vger.linux-integrity. Please address Sashiko's 2/2 review. thanks, Mimi
quoted hunk ↗ jump to hunk
--- security/integrity/ima/ima_policy.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index f79d07bb63c6fc4ba6fe594140de8d59f57e4f0b..68d9a5e6c232ea0678e9f51f105cebecccccb43e 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c@@ -165,7 +165,10 @@ static struct ima_rule_entry dont_measure_rules[] __ro_after_init = { {.action = DONT_MEASURE, .fsmagic = CGROUP2_SUPER_MAGIC, .flags = IMA_FSMAGIC}, {.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC}, - {.action = DONT_MEASURE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC} + {.action = DONT_MEASURE, .fsmagic = EFIVARFS_MAGIC, + .flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE, .fsmagic = CONFIGFS_MAGIC, + .flags = IMA_FSMAGIC} }; static struct ima_rule_entry original_measurement_rules[] __ro_after_init = {@@ -211,6 +214,8 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = { {.action = DONT_APPRAISE, .fsmagic = EFIVARFS_MAGIC, .flags = IMA_FSMAGIC}, {.action = DONT_APPRAISE, .fsmagic = CGROUP_SUPER_MAGIC, .flags = IMA_FSMAGIC}, {.action = DONT_APPRAISE, .fsmagic = CGROUP2_SUPER_MAGIC, .flags = IMA_FSMAGIC}, + {.action = DONT_APPRAISE, .fsmagic = CONFIGFS_MAGIC, + .flags = IMA_FSMAGIC}, #ifdef CONFIG_IMA_WRITE_POLICY {.action = APPRAISE, .func = POLICY_CHECK, .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},