From: Amir Goldstein <amir73il@xxxxxxxxx>
Similar to FAN_ACCESS_PERM permission event, but it is only allowed with
class FAN_CLASS_PRE_CONTENT and only allowed on regular files and dirs.
Unlike FAN_ACCESS_PERM, it is safe to write to the file being accessed
in the context of the 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 read access.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/notify/fanotify/fanotify.c | 3 ++-
fs/notify/fanotify/fanotify_user.c | 22 +++++++++++++++++++---
include/linux/fanotify.h | 14 ++++++++++----
include/uapi/linux/fanotify.h | 2 ++
4 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 2e6ba94ec405..da6c3c1c7edf 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -916,8 +916,9 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
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(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 21);
+ BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 22);
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 9cc4a9ac1515..2ec0cc9c85cf 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1633,11 +1633,23 @@ static int fanotify_events_supported(struct fsnotify_group *group,
unsigned int flags)
{
unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
+ bool is_dir = d_is_dir(path->dentry);
/* Strict validation of events in non-dir inode mask with v5.17+ APIs */
bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
(mask & FAN_RENAME) ||
(flags & FAN_MARK_IGNORE);
+ /*
+ * Filesystems need to opt-into pre-content evnets (a.k.a HSM)
+ * and they are only supported on regular files and directories.
+ */
+ if (mask & FANOTIFY_PRE_CONTENT_EVENTS) {
+ if (!(path->mnt->mnt_sb->s_iflags & SB_I_ALLOW_HSM))
+ return -EINVAL;
+ if (!is_dir && !d_is_reg(path->dentry))
+ return -EINVAL;
+ }
+
/*
* Some filesystems such as 'proc' acquire unusual locks when opening
* files. For them fanotify permission events have high chances of
@@ -1670,7 +1682,7 @@ static int fanotify_events_supported(struct fsnotify_group *group,
* but because we always allowed it, error only when using new APIs.
*/
if (strict_dir_events && mark_type == FAN_MARK_INODE &&
- !d_is_dir(path->dentry) && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
+ !is_dir && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
return -ENOTDIR;
return 0;
@@ -1771,10 +1783,14 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
return -EPERM;
/*
- * Permission events require minimum priority FAN_CLASS_CONTENT.
+ * Permission events are not allowed for FAN_CLASS_NOTIF.
+ * Pre-content permission events are not allowed for FAN_CLASS_CONTENT.
*/
if (mask & FANOTIFY_PERM_EVENTS &&
- group->priority < FSNOTIFY_PRIO_CONTENT)
+ group->priority == FSNOTIFY_PRIO_NORMAL)
+ return -EINVAL;
+ else if (mask & FANOTIFY_PRE_CONTENT_EVENTS &&
+ group->priority == FSNOTIFY_PRIO_CONTENT)
return -EINVAL;
if (mask & FAN_FS_ERROR &&
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 89ff45bd6f01..c747af064d2c 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -89,6 +89,16 @@
#define FANOTIFY_DIRENT_EVENTS (FAN_MOVE | FAN_CREATE | FAN_DELETE | \
FAN_RENAME)
+/* Content events can be used to inspect file content */
+#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)
+
+/* Events that require a permission response from user */
+#define FANOTIFY_PERM_EVENTS (FANOTIFY_CONTENT_PERM_EVENTS | \
+ FANOTIFY_PRE_CONTENT_EVENTS)
+
/* Events that can be reported with event->fd */
#define FANOTIFY_FD_EVENTS (FANOTIFY_PATH_EVENTS | FANOTIFY_PERM_EVENTS)
@@ -104,10 +114,6 @@
FANOTIFY_INODE_EVENTS | \
FANOTIFY_ERROR_EVENTS)
-/* Events that require a permission response from user */
-#define FANOTIFY_PERM_EVENTS (FAN_OPEN_PERM | FAN_ACCESS_PERM | \
- FAN_OPEN_EXEC_PERM)
-
/* Extra flags that may be reported with event or control handling of events */
#define FANOTIFY_EVENT_FLAGS (FAN_EVENT_ON_CHILD | FAN_ONDIR)
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index 79072b6894f2..7596168c80eb 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -27,6 +27,8 @@
#define FAN_OPEN_EXEC_PERM 0x00040000 /* File open/exec in perm check */
/* #define FAN_DIR_MODIFY 0x00080000 */ /* Deprecated (reserved) */
+#define FAN_PRE_ACCESS 0x00100000 /* Pre-content access hook */
+
#define FAN_EVENT_ON_CHILD 0x08000000 /* Interested in child events */
#define FAN_RENAME 0x10000000 /* File was renamed */
--
2.43.0
