diff mbox series

[v4,05/16] fanotify: introduce FAN_PRE_MODIFY permission event

Message ID 5142d1715dfecf58bc0a77eb410ca21d95e71cfc.1723670362.git.josef@toxicpanda.com (mailing list archive)
State New
Headers show
Series fanotify: add pre-content hooks | expand

Commit Message

Josef Bacik Aug. 14, 2024, 9:25 p.m. UTC 
From: Amir Goldstein <amir73il@gmail.com>

Generate FAN_PRE_MODIFY permission event from fsnotify_file_perm()
pre-write hook to notify fanotify listeners on an intent to make
modification to a file.

Like FAN_PRE_ACCESS, it is only allowed with FAN_CLASS_PRE_CONTENT
and unlike FAN_MODIFY, it is only allowed on regular files.

Like FAN_PRE_ACCESS, it is generated without sb_start_write() held,
so it is safe to perform filesystem modifications in the context of
event handler.

This pre-content event is meant to be used by hierarchical storage
managers that want to fill the content of files on first write access.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
---
 fs/notify/fanotify/fanotify.c      | 3 ++-
 fs/notify/fanotify/fanotify_user.c | 2 ++
 include/linux/fanotify.h           | 3 ++-
 include/uapi/linux/fanotify.h      | 1 +
 4 files changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 7dac8e4486df..b163594843f5 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -911,8 +911,9 @@  static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 	BUILD_BUG_ON(FAN_FS_ERROR != FS_ERROR);
 	BUILD_BUG_ON(FAN_RENAME != FS_RENAME);
 	BUILD_BUG_ON(FAN_PRE_ACCESS != FS_PRE_ACCESS);
+	BUILD_BUG_ON(FAN_PRE_MODIFY != FS_PRE_MODIFY);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 22);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 23);
 
 	mask = fanotify_group_event_mask(group, iter_info, &match_mask,
 					 mask, data, data_type, dir);
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index c294849e474f..3a7101544f30 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1673,6 +1673,8 @@  static int fanotify_events_supported(struct fsnotify_group *group,
 	if (mask & FANOTIFY_PRE_CONTENT_EVENTS) {
 		if (!is_dir && !d_is_reg(path->dentry))
 			return -EINVAL;
+		if (is_dir && mask & FAN_PRE_MODIFY)
+			return -EISDIR;
 	}
 
 	return 0;
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 5c811baf44d2..ae6cb2688d52 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -92,7 +92,8 @@ 
 #define FANOTIFY_CONTENT_PERM_EVENTS (FAN_OPEN_PERM | FAN_OPEN_EXEC_PERM | \
 				      FAN_ACCESS_PERM)
 /* Pre-content events can be used to fill file content */
-#define FANOTIFY_PRE_CONTENT_EVENTS  (FAN_PRE_ACCESS)
+#define FANOTIFY_PRE_CONTENT_EVENTS  (FAN_PRE_ACCESS | FAN_PRE_MODIFY)
+#define FANOTIFY_PRE_MODIFY_EVENTS   (FAN_PRE_MODIFY)
 
 /* Events that require a permission response from user */
 #define FANOTIFY_PERM_EVENTS	(FANOTIFY_CONTENT_PERM_EVENTS | \
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index bcada21a3a2e..ac00fad66416 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -27,6 +27,7 @@ 
 #define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
 
 #define FAN_PRE_ACCESS		0x00080000	/* Pre-content access hook */
+#define FAN_PRE_MODIFY		0x00100000	/* Pre-content modify hook */
 
 #define FAN_EVENT_ON_CHILD	0x08000000	/* Interested in child events */