fsnotify: optionally pass access range in file permission hooks

In preparation for pre-content permission events with file access range,
move fsnotify_file_perm() hook out of security_file_permission() and into
the callers.

Callers that have the access range information call the new hook
fsnotify_file_area_perm() with the access range.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231212094440.250945-6-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

6 files changed, 35 insertions, 12 deletions

diff --git a/fs/open.c b/fs/open.c
index 02dc608d40d8..d877228d5939 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -304,6 +304,10 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	if (ret)
 		return ret;
 
+	ret = fsnotify_file_area_perm(file, MAY_WRITE, &offset, len);
+	if (ret)
+		return ret;
+
 	if (S_ISFIFO(inode->i_mode))
 		return -ESPIPE;
 
diff --git a/fs/read_write.c b/fs/read_write.c
index e3abf603eaaf..d4c036e82b6c 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -354,6 +354,9 @@ out_putf:
 
 int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t count)
 {
+	int mask = read_write == READ ? MAY_READ : MAY_WRITE;
+	int ret;
+
 	if (unlikely((ssize_t) count < 0))
 		return -EINVAL;
 
@@ -371,8 +374,11 @@ int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t
 		}
 	}
 
-	return security_file_permission(file,
-				read_write == READ ? MAY_READ : MAY_WRITE);
+	ret = security_file_permission(file, mask);
+	if (ret)
+		return ret;
+
+	return fsnotify_file_area_perm(file, mask, ppos, count);
 }
 EXPORT_SYMBOL(rw_verify_area);
 
diff --git a/fs/readdir.c b/fs/readdir.c
index c8c46e294431..278bc0254732 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -96,6 +96,10 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 	if (res)
 		goto out;
 
+	res = fsnotify_file_perm(file, MAY_READ);
+	if (res)
+		goto out;
+
 	res = down_read_killable(&inode->i_rwsem);
 	if (res)
 		goto out;
diff --git a/fs/remap_range.c b/fs/remap_range.c
index 12131f2a6c9e..f8c1120b8311 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -102,7 +102,9 @@ static int generic_remap_checks(struct file *file_in, loff_t pos_in,
 static int remap_verify_area(struct file *file, loff_t pos, loff_t len,
 			     bool write)
 {
+	int mask = write ? MAY_WRITE : MAY_READ;
 	loff_t tmp;
+	int ret;
 
 	if (unlikely(pos < 0 || len < 0))
 		return -EINVAL;
@@ -110,7 +112,11 @@ static int remap_verify_area(struct file *file, loff_t pos, loff_t len,
 	if (unlikely(check_add_overflow(pos, len, &tmp)))
 		return -EINVAL;
 
-	return security_file_permission(file, write ? MAY_WRITE : MAY_READ);
+	ret = security_file_permission(file, mask);
+	if (ret)
+		return ret;
+
+	return fsnotify_file_area_perm(file, mask, &pos, len);
 }
 
 /*
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 0a9d6a8a747a..11e6434b8e71 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -101,9 +101,10 @@ static inline int fsnotify_file(struct file *file, __u32 mask)
 }
 
 /*
- * fsnotify_file_perm - permission hook before file access
+ * fsnotify_file_area_perm - permission hook before access to file range
  */
-static inline int fsnotify_file_perm(struct file *file, int perm_mask)
+static inline int fsnotify_file_area_perm(struct file *file, int perm_mask,
+					  const loff_t *ppos, size_t count)
 {
 	__u32 fsnotify_mask = FS_ACCESS_PERM;
 
@@ -121,6 +122,14 @@ static inline int fsnotify_file_perm(struct file *file, int perm_mask)
 }
 
 /*
+ * fsnotify_file_perm - permission hook before file access
+ */
+static inline int fsnotify_file_perm(struct file *file, int perm_mask)
+{
+	return fsnotify_file_area_perm(file, perm_mask, NULL, 0);
+}
+
+/*
  * fsnotify_open_perm - permission hook before file open
  */
 static inline int fsnotify_open_perm(struct file *file)
diff --git a/security/security.c b/security/security.c
index d7f3703c5905..2a7fc7881cbc 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2580,13 +2580,7 @@ int security_kernfs_init_security(struct kernfs_node *kn_dir,
  */
 int security_file_permission(struct file *file, int mask)
 {
-	int ret;
-
-	ret = call_int_hook(file_permission, 0, file, mask);
-	if (ret)
-		return ret;
-
-	return fsnotify_file_perm(file, mask);
+	return call_int_hook(file_permission, 0, file, mask);
 }
 
 /**