From f4fee216df7d28b87d1c9cc60bcebfecb51c1a05 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjguzik@gmail.com>
Date: Thu, 20 Jun 2024 19:15:27 +0200
Subject: [PATCH] apparmor: try to avoid refing the label in apparmor_file_open
If the label is not stale (which is the common case), the fact that the
passed file object holds a reference can be leverged to avoid the
ref/unref cycle. Doing so reduces performance impact of apparmor on
parallel open() invocations.
When benchmarking on a 24-core vm using will-it-scale's open1_process
("Separate file open"), the results are (ops/s):
before: 6092196
after: 8309726 (+36%)
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
---
security/apparmor/include/cred.h | 20 ++++++++++++++++++++
security/apparmor/lsm.c | 5 +++--
2 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/security/apparmor/include/cred.h b/security/apparmor/include/cred.h
index 58fdc72af6645..7265d2f81dd50 100644
--- a/security/apparmor/include/cred.h
+++ b/security/apparmor/include/cred.h
@@ -63,6 +63,26 @@ static inline struct aa_label *aa_get_newest_cred_label(const struct cred *cred)
return aa_get_newest_label(aa_cred_raw_label(cred));
}
+static inline struct aa_label *aa_get_newest_cred_label_condref(const struct cred *cred,
+ bool *needput)
+{
+ struct aa_label *l = aa_cred_raw_label(cred);
+
+ if (unlikely(label_is_stale(l))) {
+ *needput = true;
+ return aa_get_newest_label(l);
+ }
+
+ *needput = false;
+ return l;
+}
+
+static inline void aa_put_label_condref(struct aa_label *l, bool needput)
+{
+ if (unlikely(needput))
+ aa_put_label(l);
+}
+
/**
* aa_current_raw_label - find the current tasks confining label
*
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 717204fba938b..242d4cf857a7b 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -461,6 +461,7 @@ static int apparmor_file_open(struct file *file)
struct aa_file_ctx *fctx = file_ctx(file);
struct aa_label *label;
int error = 0;
+ bool needput;
if (!path_mediated_fs(file->f_path.dentry))
return 0;
@@ -477,7 +478,7 @@ static int apparmor_file_open(struct file *file)
return 0;
}
- label = aa_get_newest_cred_label(file->f_cred);
+ label = aa_get_newest_cred_label_condref(file->f_cred, &needput);
if (!unconfined(label)) {
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);
@@ -494,7 +495,7 @@ static int apparmor_file_open(struct file *file)
/* todo cache full allowed permissions set and state */
fctx->allow = aa_map_file_to_perms(file);
}
- aa_put_label(label);
+ aa_put_label_condref(label, needput);
return error;
}
--
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