diff mbox series

[v7,22/28] fanotify: Report FID entry even for zero-length file_handle

Message ID 20211014213646.1139469-23-krisman@collabora.com (mailing list archive)
State New, archived
Headers show
Series file system-wide error monitoring | expand

Commit Message

Gabriel Krisman Bertazi Oct. 14, 2021, 9:36 p.m. UTC 
Non-inode errors will reported with an empty file_handle.  In
preparation for that, allow some events to print the FID record even if
there isn't any file_handle encoded

Even though FILEID_ROOT is used internally, make zero-length file
handles be reported as FILEID_INVALID.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
---
 fs/notify/fanotify/fanotify_user.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

Comments

Amir Goldstein Oct. 15, 2021, 8:10 a.m. UTC | #1 
On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
<krisman@collabora.com> wrote:
>
> Non-inode errors will reported with an empty file_handle.  In
> preparation for that, allow some events to print the FID record even if
> there isn't any file_handle encoded
>
> Even though FILEID_ROOT is used internally, make zero-length file
> handles be reported as FILEID_INVALID.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> ---
>  fs/notify/fanotify/fanotify_user.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 5324890500fc..39cf8ba4a6ce 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -127,6 +127,16 @@ static int fanotify_fid_info_len(int fh_len, int name_len)
>                        FANOTIFY_EVENT_ALIGN);
>  }
>
> +static bool fanotify_event_allows_empty_fh(struct fanotify_event *event)
> +{
> +       switch (event->type) {
> +       case FANOTIFY_EVENT_TYPE_FS_ERROR:
> +               return true;
> +       default:
> +               return false;
> +       }
> +}
> +
>  static size_t fanotify_event_len(unsigned int info_mode,
>                                  struct fanotify_event *event)
>  {
> @@ -157,7 +167,7 @@ static size_t fanotify_event_len(unsigned int info_mode,
>         if (info_mode & FAN_REPORT_PIDFD)
>                 event_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
>
> -       if (fh_len)
> +       if (fh_len || fanotify_event_allows_empty_fh(event))
>                 event_len += fanotify_fid_info_len(fh_len, dot_len);
>
>         return event_len;
> @@ -338,9 +348,6 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>         pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
>                  __func__, fh_len, name_len, info_len, count);
>
> -       if (!fh_len)
> -               return 0;
> -
>         if (WARN_ON_ONCE(len < sizeof(info) || len > count))
>                 return -EFAULT;
>
> @@ -375,6 +382,11 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>
>         handle.handle_type = fh->type;
>         handle.handle_bytes = fh_len;
> +
> +       /* Mangle handle_type for bad file_handle */
> +       if (!fh_len)
> +               handle.handle_type = FILEID_INVALID;
> +
>         if (copy_to_user(buf, &handle, sizeof(handle)))
>                 return -EFAULT;
>
> @@ -467,7 +479,8 @@ static int copy_info_records_to_user(struct fanotify_event *event,
>                 total_bytes += ret;
>         }
>
> -       if (fanotify_event_object_fh_len(event)) {
> +       if (fanotify_event_object_fh_len(event) ||
> +           fanotify_event_allows_empty_fh(event)) {
>                 const char *dot = NULL;
>                 int dot_len = 0;
>

I don't like this fanotify_event_allows_empty_fh() implementation so much.

How about this instead:

static inline struct fanotify_fh *fanotify_event_object_fh(
                                                struct fanotify_event *event)
{
        struct fanotify_fh *fh = NULL;

        /* An error event encodes (a FILEID_INVAL) fh for an empty fh */
        if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
                return &FANOTIFY_EE(event)->object_fh;
        else if (event->type == FANOTIFY_EVENT_TYPE_FID)
                fh = &FANOTIFY_FE(event)->object_fh;
        else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
                fh = fanotify_info_file_fh(&FANOTIFY_NE(event)->info);

        if (!fh && !fh->len)
                return NULL;

        return fh;
}

        struct fanotify_fh *object_fh = fanotify_event_object_fh(event);
...

-       if (fanotify_event_object_fh_len(event)) {
+       if (object_fh) {
                const char *dot = NULL;
...
                ret = copy_fid_info_to_user(fanotify_event_fsid(event),
-                                           fanotify_event_object_fh(event),
+                                          object_fh,
                                            info_type, dot, dot_len,
                                            buf, count);
...

And similar change to fanotify_event_len()

This way, the logic of whether to report fh or not is encoded in
fanotify_event_object_fh() and fanotify_event_object_fh_len()
goes back to being a property of the the fh report.

Thanks,
Amir.
Jan Kara Oct. 15, 2021, 1:13 p.m. UTC | #2 
On Fri 15-10-21 11:10:58, Amir Goldstein wrote:
> On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
> <krisman@collabora.com> wrote:
> >
> > Non-inode errors will reported with an empty file_handle.  In
> > preparation for that, allow some events to print the FID record even if
> > there isn't any file_handle encoded
> >
> > Even though FILEID_ROOT is used internally, make zero-length file
> > handles be reported as FILEID_INVALID.
> >
> > Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> > ---
> >  fs/notify/fanotify/fanotify_user.c | 23 ++++++++++++++++++-----
> >  1 file changed, 18 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> > index 5324890500fc..39cf8ba4a6ce 100644
> > --- a/fs/notify/fanotify/fanotify_user.c
> > +++ b/fs/notify/fanotify/fanotify_user.c
> > @@ -127,6 +127,16 @@ static int fanotify_fid_info_len(int fh_len, int name_len)
> >                        FANOTIFY_EVENT_ALIGN);
> >  }
> >
> > +static bool fanotify_event_allows_empty_fh(struct fanotify_event *event)
> > +{
> > +       switch (event->type) {
> > +       case FANOTIFY_EVENT_TYPE_FS_ERROR:
> > +               return true;
> > +       default:
> > +               return false;
> > +       }
> > +}
> > +
> >  static size_t fanotify_event_len(unsigned int info_mode,
> >                                  struct fanotify_event *event)
> >  {
> > @@ -157,7 +167,7 @@ static size_t fanotify_event_len(unsigned int info_mode,
> >         if (info_mode & FAN_REPORT_PIDFD)
> >                 event_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
> >
> > -       if (fh_len)
> > +       if (fh_len || fanotify_event_allows_empty_fh(event))
> >                 event_len += fanotify_fid_info_len(fh_len, dot_len);
> >
> >         return event_len;
> > @@ -338,9 +348,6 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
> >         pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
> >                  __func__, fh_len, name_len, info_len, count);
> >
> > -       if (!fh_len)
> > -               return 0;
> > -
> >         if (WARN_ON_ONCE(len < sizeof(info) || len > count))
> >                 return -EFAULT;
> >
> > @@ -375,6 +382,11 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
> >
> >         handle.handle_type = fh->type;
> >         handle.handle_bytes = fh_len;
> > +
> > +       /* Mangle handle_type for bad file_handle */
> > +       if (!fh_len)
> > +               handle.handle_type = FILEID_INVALID;
> > +
> >         if (copy_to_user(buf, &handle, sizeof(handle)))
> >                 return -EFAULT;
> >
> > @@ -467,7 +479,8 @@ static int copy_info_records_to_user(struct fanotify_event *event,
> >                 total_bytes += ret;
> >         }
> >
> > -       if (fanotify_event_object_fh_len(event)) {
> > +       if (fanotify_event_object_fh_len(event) ||
> > +           fanotify_event_allows_empty_fh(event)) {
> >                 const char *dot = NULL;
> >                 int dot_len = 0;
> >
> 
> I don't like this fanotify_event_allows_empty_fh() implementation so much.
> 
> How about this instead:
> 
> static inline struct fanotify_fh *fanotify_event_object_fh(
>                                                 struct fanotify_event *event)
> {
>         struct fanotify_fh *fh = NULL;
> 
>         /* An error event encodes (a FILEID_INVAL) fh for an empty fh */
>         if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
>                 return &FANOTIFY_EE(event)->object_fh;
>         else if (event->type == FANOTIFY_EVENT_TYPE_FID)
>                 fh = &FANOTIFY_FE(event)->object_fh;
>         else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
>                 fh = fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
> 
>         if (!fh && !fh->len)
>                 return NULL;
> 
>         return fh;
> }
> 
>         struct fanotify_fh *object_fh = fanotify_event_object_fh(event);
> ...
> 
> -       if (fanotify_event_object_fh_len(event)) {
> +       if (object_fh) {
>                 const char *dot = NULL;
> ...
>                 ret = copy_fid_info_to_user(fanotify_event_fsid(event),
> -                                           fanotify_event_object_fh(event),
> +                                          object_fh,
>                                             info_type, dot, dot_len,
>                                             buf, count);
> ...
> 
> And similar change to fanotify_event_len()
> 
> This way, the logic of whether to report fh or not is encoded in
> fanotify_event_object_fh() and fanotify_event_object_fh_len()
> goes back to being a property of the the fh report.

I like this except that AFAICT this will be problematic for
fanotify_event_object_fh_len() because there we want to return 0 (length of
file handle buffer to copy) for error events - so "copy just header to
userspace" is going to be indistiguishable from "copy nothing".

But maybe we need helpers fanotify_event_has_object_fh() and
fanotify_event_has_dir_fh() (for symmetry) instead of directly checking
fh_len? These would then encapsulate all the magic for error events.

								Honza
diff mbox series

Patch

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 5324890500fc..39cf8ba4a6ce 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -127,6 +127,16 @@  static int fanotify_fid_info_len(int fh_len, int name_len)
 		       FANOTIFY_EVENT_ALIGN);
 }
 
+static bool fanotify_event_allows_empty_fh(struct fanotify_event *event)
+{
+	switch (event->type) {
+	case FANOTIFY_EVENT_TYPE_FS_ERROR:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static size_t fanotify_event_len(unsigned int info_mode,
 				 struct fanotify_event *event)
 {
@@ -157,7 +167,7 @@  static size_t fanotify_event_len(unsigned int info_mode,
 	if (info_mode & FAN_REPORT_PIDFD)
 		event_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
 
-	if (fh_len)
+	if (fh_len || fanotify_event_allows_empty_fh(event))
 		event_len += fanotify_fid_info_len(fh_len, dot_len);
 
 	return event_len;
@@ -338,9 +348,6 @@  static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
 	pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
 		 __func__, fh_len, name_len, info_len, count);
 
-	if (!fh_len)
-		return 0;
-
 	if (WARN_ON_ONCE(len < sizeof(info) || len > count))
 		return -EFAULT;
 
@@ -375,6 +382,11 @@  static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
 
 	handle.handle_type = fh->type;
 	handle.handle_bytes = fh_len;
+
+	/* Mangle handle_type for bad file_handle */
+	if (!fh_len)
+		handle.handle_type = FILEID_INVALID;
+
 	if (copy_to_user(buf, &handle, sizeof(handle)))
 		return -EFAULT;
 
@@ -467,7 +479,8 @@  static int copy_info_records_to_user(struct fanotify_event *event,
 		total_bytes += ret;
 	}
 
-	if (fanotify_event_object_fh_len(event)) {
+	if (fanotify_event_object_fh_len(event) ||
+	    fanotify_event_allows_empty_fh(event)) {
 		const char *dot = NULL;
 		int dot_len = 0;