linux-kernel - [PATCH v2 2/4] pstore: inode: Convert mutex usage to guard(mutex)

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Message-Id: <20231205182622.1329923-2-keescook@chromium.org>
Date:   Tue,  5 Dec 2023 10:26:15 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] pstore: inode: Convert mutex usage to guard(mutex)

Replace open-coded mutex handling with cleanup.h guard(mutex) and
scoped_guard(mutex, ...).

Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/pstore/inode.c | 76 +++++++++++++++++++----------------------------
 1 file changed, 31 insertions(+), 45 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 20f3452c8196..0d89e0014b6f 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -180,25 +180,21 @@ static int pstore_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct pstore_private *p = d_inode(dentry)->i_private;
 	struct pstore_record *record = p->record;
-	int rc = 0;
 
 	if (!record->psi->erase)
 		return -EPERM;
 
 	/* Make sure we can't race while removing this file. */
-	mutex_lock(&records_list_lock);
-	if (!list_empty(&p->list))
-		list_del_init(&p->list);
-	else
-		rc = -ENOENT;
-	p->dentry = NULL;
-	mutex_unlock(&records_list_lock);
-	if (rc)
-		return rc;
-
-	mutex_lock(&record->psi->read_mutex);
-	record->psi->erase(record);
-	mutex_unlock(&record->psi->read_mutex);
+	scoped_guard(mutex, &records_list_lock) {
+		if (!list_empty(&p->list))
+			list_del_init(&p->list);
+		else
+			return -ENOENT;
+		p->dentry = NULL;
+	}
+
+	scoped_guard(mutex, &record->psi->read_mutex)
+		record->psi->erase(record);
 
 	return simple_unlink(dir, dentry);
 }
@@ -290,19 +286,16 @@ static struct dentry *psinfo_lock_root(void)
 {
 	struct dentry *root;
 
-	mutex_lock(&pstore_sb_lock);
+	guard(mutex)(&pstore_sb_lock);
 	/*
 	 * Having no backend is fine -- no records appear.
 	 * Not being mounted is fine -- nothing to do.
 	 */
-	if (!psinfo || !pstore_sb) {
-		mutex_unlock(&pstore_sb_lock);
+	if (!psinfo || !pstore_sb)
 		return NULL;
-	}
 
 	root = pstore_sb->s_root;
 	inode_lock(d_inode(root));
-	mutex_unlock(&pstore_sb_lock);
 
 	return root;
 }
@@ -317,19 +310,19 @@ int pstore_put_backend_records(struct pstore_info *psi)
 	if (!root)
 		return 0;
 
-	mutex_lock(&records_list_lock);
-	list_for_each_entry_safe(pos, tmp, &records_list, list) {
-		if (pos->record->psi == psi) {
-			list_del_init(&pos->list);
-			rc = simple_unlink(d_inode(root), pos->dentry);
-			if (WARN_ON(rc))
-				break;
-			d_drop(pos->dentry);
-			dput(pos->dentry);
-			pos->dentry = NULL;
+	scoped_guard(mutex, &records_list_lock) {
+		list_for_each_entry_safe(pos, tmp, &records_list, list) {
+			if (pos->record->psi == psi) {
+				list_del_init(&pos->list);
+				rc = simple_unlink(d_inode(root), pos->dentry);
+				if (WARN_ON(rc))
+					break;
+				d_drop(pos->dentry);
+				dput(pos->dentry);
+				pos->dentry = NULL;
+			}
 		}
 	}
-	mutex_unlock(&records_list_lock);
 
 	inode_unlock(d_inode(root));
 
@@ -353,20 +346,20 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	if (WARN_ON(!inode_is_locked(d_inode(root))))
 		return -EINVAL;
 
-	rc = -EEXIST;
+	guard(mutex)(&records_list_lock);
+
 	/* Skip records that are already present in the filesystem. */
-	mutex_lock(&records_list_lock);
 	list_for_each_entry(pos, &records_list, list) {
 		if (pos->record->type == record->type &&
 		    pos->record->id == record->id &&
 		    pos->record->psi == record->psi)
-			goto fail;
+			return -EEXIST;
 	}
 
 	rc = -ENOMEM;
 	inode = pstore_get_inode(root->d_sb);
 	if (!inode)
-		goto fail;
+		return -ENOMEM;
 	inode->i_mode = S_IFREG | 0444;
 	inode->i_fop = &pstore_file_operations;
 	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
@@ -394,7 +387,6 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	d_add(dentry, inode);
 
 	list_add(&private->list, &records_list);
-	mutex_unlock(&records_list_lock);
 
 	return 0;
 
@@ -402,8 +394,6 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	free_pstore_private(private);
 fail_inode:
 	iput(inode);
-fail:
-	mutex_unlock(&records_list_lock);
 	return rc;
 }
 
@@ -449,9 +439,8 @@ static int pstore_fill_super(struct super_block *sb, void *data, int silent)
 	if (!sb->s_root)
 		return -ENOMEM;
 
-	mutex_lock(&pstore_sb_lock);
-	pstore_sb = sb;
-	mutex_unlock(&pstore_sb_lock);
+	scoped_guard(mutex, &pstore_sb_lock)
+		pstore_sb = sb;
 
 	pstore_get_records(0);
 
@@ -466,17 +455,14 @@ static struct dentry *pstore_mount(struct file_system_type *fs_type,
 
 static void pstore_kill_sb(struct super_block *sb)
 {
-	mutex_lock(&pstore_sb_lock);
+	guard(mutex)(&pstore_sb_lock);
 	WARN_ON(pstore_sb && pstore_sb != sb);
 
 	kill_litter_super(sb);
 	pstore_sb = NULL;
 
-	mutex_lock(&records_list_lock);
+	guard(mutex)(&records_list_lock);
 	INIT_LIST_HEAD(&records_list);
-	mutex_unlock(&records_list_lock);
-
-	mutex_unlock(&pstore_sb_lock);
 }
 
 static struct file_system_type pstore_fs_type = {
-- 
2.34.1