Introduce a new flag FAN_REPORT_PIDFD for fanotify_init(2) which
allows userspace applications to control whether a pidfd info record
containing a pidfd is to be returned with each event.
If FAN_REPORT_PIDFD is enabled for a notification group, an additional
struct fanotify_event_info_pidfd object will be supplied alongside the
generic struct fanotify_event_metadata within a single event. This
functionality is analogous to that of FAN_REPORT_FID in terms of how
the event structure is supplied to the userspace application. Usage of
FAN_REPORT_PIDFD with FAN_REPORT_FID/FAN_REPORT_DFID_NAME is
permitted, and in this case a struct fanotify_event_info_pidfd object
will follow any struct fanotify_event_info_fid object.
Usage of FAN_REPORT_TID is not permitted with FAN_REPORT_PIDFD as the
pidfd API only supports the creation of pidfds for thread-group
leaders. Attempting to do so will result with a -EINVAL being returned
when calling fanotify_init(2).
If pidfd creation fails via pidfd_create(), the pidfd field within
struct fanotify_event_info_pidfd is set to FAN_NOPIDFD.
Signed-off-by: Matthew Bobrowski <repnop@xxxxxxxxxx>
---
fs/notify/fanotify/fanotify_user.c | 65 +++++++++++++++++++++++++++---
include/linux/fanotify.h | 3 +-
include/uapi/linux/fanotify.h | 12 ++++++
3 files changed, 74 insertions(+), 6 deletions(-)
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 1e15f3222eb2..bba61988f4a0 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -106,6 +106,8 @@ struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
#define FANOTIFY_EVENT_ALIGN 4
#define FANOTIFY_FID_INFO_HDR_LEN \
(sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
+#define FANOTIFY_PIDFD_INFO_HDR_LEN \
+ sizeof(struct fanotify_event_info_pidfd)
static int fanotify_fid_info_len(int fh_len, int name_len)
{
@@ -141,6 +143,9 @@ static int fanotify_event_info_len(unsigned int info_mode,
if (fh_len)
info_len += fanotify_fid_info_len(fh_len, dot_len);
+ if (info_mode & FAN_REPORT_PIDFD)
+ info_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
+
return info_len;
}
@@ -401,6 +406,29 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid,
return info_len;
}
+static int copy_pidfd_info_to_user(struct pid *pid,
+ char __user *buf,
+ size_t count)
+{
+ struct fanotify_event_info_pidfd info = { };
+ size_t info_len = FANOTIFY_PIDFD_INFO_HDR_LEN;
+
+ if (WARN_ON_ONCE(info_len > count))
+ return -EFAULT;
+
+ info.hdr.info_type = FAN_EVENT_INFO_TYPE_PIDFD;
+ info.hdr.len = info_len;
+
+ info.pidfd = pidfd_create(pid, 0);
+ if (info.pidfd < 0)
+ info.pidfd = FAN_NOPIDFD;
+
+ if (copy_to_user(buf, &info, info_len))
+ return -EFAULT;
+
+ return info_len;
+}
+
static int copy_info_to_user(struct fanotify_event *event,
struct fanotify_info *info,
unsigned int info_mode,
@@ -408,9 +436,12 @@ static int copy_info_to_user(struct fanotify_event *event,
{
int ret, info_type = 0;
unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;
+ unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
/*
* Event info records order is as follows: dir fid + name, child fid.
+ * If FAN_REPORT_PIDFD has been specified, then a pidfd info record
+ * will follow the fid info records.
*/
if (fanotify_event_dir_fh_len(event)) {
info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
@@ -465,10 +496,18 @@ static int copy_info_to_user(struct fanotify_event *event,
}
ret = copy_fid_info_to_user(fanotify_event_fsid(event),
- fanotify_event_object_fh(event),
- info_type, dot, dot_len,
- buf, count);
- }
+ fanotify_event_object_fh(event),
+ info_type, dot, dot_len,
+ buf, count);
+ if (ret < 0)
+ return ret;
+
+ buf += ret;
+ count -= ret;
+ }
+
+ if (pidfd_mode)
+ return copy_pidfd_info_to_user(event->pid, buf, count);
return ret;
}
@@ -530,6 +569,15 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
fd_install(fd, f);
if (info_mode) {
+ /*
+ * Complain if FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
+ * exclusion is ever lifted. At the time of implementing
+ * FAN_REPORT_PIDFD, the pidfd API only supported the creation
+ * of pidfds on thread-group leaders.
+ */
+ WARN_ON_ONCE((info_mode & FAN_REPORT_PIDFD) &&
+ FAN_GROUP_FLAG(group, FAN_REPORT_TID));
+
ret = copy_info_to_user(event, info, info_mode, buf, count);
if (ret < 0)
return ret;
@@ -1079,6 +1127,13 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
#endif
return -EINVAL;
+ /*
+ * A pidfd can only be returned for a thread-group leader; thus
+ * FAN_REPORT_TID and FAN_REPORT_PIDFD need to be mutually exclusive.
+ */
+ if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
+ return -EINVAL;
+
if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
return -EINVAL;
@@ -1477,7 +1532,7 @@ static int __init fanotify_user_setup(void)
max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
FANOTIFY_DEFAULT_MAX_USER_MARKS);
- BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10);
+ BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 11);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index f76c7635efc8..bb2898240e5a 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -27,7 +27,7 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
#define FANOTIFY_FID_BITS (FAN_REPORT_FID | FAN_REPORT_DFID_NAME)
-#define FANOTIFY_INFO_MODES (FANOTIFY_FID_BITS)
+#define FANOTIFY_INFO_MODES (FANOTIFY_FID_BITS | FAN_REPORT_PIDFD)
/*
* fanotify_init() flags that require CAP_SYS_ADMIN.
@@ -37,6 +37,7 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
*/
#define FANOTIFY_ADMIN_INIT_FLAGS (FANOTIFY_PERM_CLASSES | \
FAN_REPORT_TID | \
+ FAN_REPORT_PIDFD | \
FAN_UNLIMITED_QUEUE | \
FAN_UNLIMITED_MARKS)
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index fbf9c5c7dd59..36c3bddcf690 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -55,6 +55,7 @@
#define FAN_REPORT_FID 0x00000200 /* Report unique file id */
#define FAN_REPORT_DIR_FID 0x00000400 /* Report unique directory id */
#define FAN_REPORT_NAME 0x00000800 /* Report events with name */
+#define FAN_REPORT_PIDFD 0x00001000 /* Report pidfd for event->pid */
/* Convenience macro - FAN_REPORT_NAME requires FAN_REPORT_DIR_FID */
#define FAN_REPORT_DFID_NAME (FAN_REPORT_DIR_FID | FAN_REPORT_NAME)
@@ -123,6 +124,7 @@ struct fanotify_event_metadata {
#define FAN_EVENT_INFO_TYPE_FID 1
#define FAN_EVENT_INFO_TYPE_DFID_NAME 2
#define FAN_EVENT_INFO_TYPE_DFID 3
+#define FAN_EVENT_INFO_TYPE_PIDFD 4
/* Variable length info record following event metadata */
struct fanotify_event_info_header {
@@ -148,6 +150,15 @@ struct fanotify_event_info_fid {
unsigned char handle[0];
};
+/*
+ * This structure is used for info records of type FAN_EVENT_INFO_TYPE_PIDFD.
+ * It holds a pidfd for the pid responsible for generating an event.
+ */
+struct fanotify_event_info_pidfd {
+ struct fanotify_event_info_header hdr;
+ __s32 pidfd;
+};
+
struct fanotify_response {
__s32 fd;
__u32 response;
@@ -160,6 +171,7 @@ struct fanotify_response {
/* No fd set in event */
#define FAN_NOFD -1
+#define FAN_NOPIDFD FAN_NOFD
/* Helper functions to deal with fanotify_event_metadata buffers */
#define FAN_EVENT_METADATA_LEN (sizeof(struct fanotify_event_metadata))
--
2.31.1.751.gd2f1c929bd-goog
/M
