fanotify: Emit generic error info for error event

The error info is a record sent to users on FAN_FS_ERROR events
documenting the type of error.  It also carries an error count,
documenting how many errors were observed since the last reporting.

Link: https://lore.kernel.org/r/20211025192746.66445-28-krisman@collabora.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 465f07e..af61425 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -621,6 +621,7 @@ static struct fanotify_event *fanotify_alloc_error_event(
                return NULL;
 
        fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
+       fee->error = report->error;
        fee->err_count = 1;
        fee->fsid = *fsid;
 

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index edd7587..d25f500 100644 (file)
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -205,6 +205,7 @@ FANOTIFY_NE(struct fanotify_event *event)
 
 struct fanotify_error_event {
        struct fanotify_event fae;
+       s32 error; /* Error reported by the Filesystem. */
        u32 err_count; /* Suppressed errors count */
 
        __kernel_fsid_t fsid; /* FSID this error refers to. */

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index ff4a737..fb81702 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -115,6 +115,8 @@ struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
        (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
 #define FANOTIFY_PIDFD_INFO_HDR_LEN \
        sizeof(struct fanotify_event_info_pidfd)
+#define FANOTIFY_ERROR_INFO_LEN \
+       (sizeof(struct fanotify_event_info_error))
 
 static int fanotify_fid_info_len(int fh_len, int name_len)
 {
@@ -139,6 +141,9 @@ static size_t fanotify_event_len(unsigned int info_mode,
        if (!info_mode)
                return event_len;
 
+       if (fanotify_is_error_event(event->mask))
+               event_len += FANOTIFY_ERROR_INFO_LEN;
+
        info = fanotify_event_info(event);
 
        if (fanotify_event_has_dir_fh(event)) {
@@ -324,6 +329,28 @@ static int process_access_response(struct fsnotify_group *group,
        return -ENOENT;
 }
 
+static size_t copy_error_info_to_user(struct fanotify_event *event,
+                                     char __user *buf, int count)
+{
+       struct fanotify_event_info_error info;
+       struct fanotify_error_event *fee = FANOTIFY_EE(event);
+
+       info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
+       info.hdr.pad = 0;
+       info.hdr.len = FANOTIFY_ERROR_INFO_LEN;
+
+       if (WARN_ON(count < info.hdr.len))
+               return -EFAULT;
+
+       info.error = fee->error;
+       info.error_count = fee->err_count;
+
+       if (copy_to_user(buf, &info, sizeof(info)))
+               return -EFAULT;
+
+       return info.hdr.len;
+}
+
 static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
                                 int info_type, const char *name,
                                 size_t name_len,
@@ -530,6 +557,15 @@ static int copy_info_records_to_user(struct fanotify_event *event,
                total_bytes += ret;
        }
 
+       if (fanotify_is_error_event(event->mask)) {
+               ret = copy_error_info_to_user(event, buf, count);
+               if (ret < 0)
+                       return ret;
+               buf += ret;
+               count -= ret;
+               total_bytes += ret;
+       }
+
        return total_bytes;
 }
 

diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index 2990731..bd1932c 100644 (file)
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -126,6 +126,7 @@ struct fanotify_event_metadata {
 #define FAN_EVENT_INFO_TYPE_DFID_NAME  2
 #define FAN_EVENT_INFO_TYPE_DFID       3
 #define FAN_EVENT_INFO_TYPE_PIDFD      4
+#define FAN_EVENT_INFO_TYPE_ERROR      5
 
 /* Variable length info record following event metadata */
 struct fanotify_event_info_header {
@@ -160,6 +161,12 @@ struct fanotify_event_info_pidfd {
        __s32 pidfd;
 };
 
+struct fanotify_event_info_error {
+       struct fanotify_event_info_header hdr;
+       __s32 error;
+       __u32 error_count;
+};
+
 struct fanotify_response {
        __s32 fd;
        __u32 response;