linux-kernel - [PATCH] fsnotify, lsm: Separate fsnotify_open_perm() and security_file

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Message-ID: <20241011203722.3749850-1-song@kernel.org>
Date: Fri, 11 Oct 2024 13:37:22 -0700
From: Song Liu <song@...nel.org>
To: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	paul@...l-moore.com,
	jmorris@...ei.org,
	serge@...lyn.com,
	kernel-team@...com,
	song@...nel.org
Subject: [PATCH] fsnotify, lsm: Separate fsnotify_open_perm() and security_file_open()

Currently, fsnotify_open_perm() is called from security_file_open(). This
is not right for CONFIG_SECURITY=n and CONFIG_FSNOTIFY=y case, as
security_file_open() in this combination will be a no-op and not call
fsnotify_open_perm(). Fix this by calling fsnotify_open_perm() directly.

Signed-off-by: Song Liu <song@...nel.org>

---

PS: I didn't included a Fixes tag. This issue was probably introduced 15
years ago in [1]. If we want to back port this to stable, we will need
another version for older kernel because of [2].

[1] c4ec54b40d33 ("fsnotify: new fsnotify hooks and events types for access decisions")
[2] 36e28c42187c ("fsnotify: split fsnotify_perm() into two hooks")
---
 fs/open.c           | 4 ++++
 security/security.c | 9 +--------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index acaeb3e25c88..6c4950f19cfb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -946,6 +946,10 @@ static int do_dentry_open(struct file *f,
 	if (error)
 		goto cleanup_all;
 
+	error = fsnotify_open_perm(f);
+	if (error)
+		goto cleanup_all;
+
 	error = break_lease(file_inode(f), f->f_flags);
 	if (error)
 		goto cleanup_all;
diff --git a/security/security.c b/security/security.c
index 6875eb4a59fc..a72cc62c0a07 100644
--- a/security/security.c
+++ b/security/security.c
@@ -19,7 +19,6 @@
 #include <linux/kernel.h>
 #include <linux/kernel_read_file.h>
 #include <linux/lsm_hooks.h>
-#include <linux/fsnotify.h>
 #include <linux/mman.h>
 #include <linux/mount.h>
 #include <linux/personality.h>
@@ -3102,13 +3101,7 @@ int security_file_receive(struct file *file)
  */
 int security_file_open(struct file *file)
 {
-	int ret;
-
-	ret = call_int_hook(file_open, file);
-	if (ret)
-		return ret;
-
-	return fsnotify_open_perm(file);
+	return call_int_hook(file_open, file);
 }
 
 /**
-- 
2.43.5