fanotify: Report fid info for file related file system errors

Plumb the pieces to add a FID report to error records.  Since all error
event memory must be pre-allocated, we pre-allocate the maximum file
handle size possible, such that it should always fit.

For errors that don't expose a file handle, report it with an invalid
FID. Internally we use zero-length FILEID_ROOT file handle for passing
the information (which we report as zero-length FILEID_INVALID file
handle to userspace) so we update the handle reporting code to deal with
this case correctly.

Link: https://lore.kernel.org/r/20211025192746.66445-27-krisman@collabora.com
Link: https://lore.kernel.org/r/20211025192746.66445-25-krisman@collabora.com
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
[Folded two patches into 2 to make series bisectable]
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 45df610..465f07e 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -609,7 +609,9 @@ static struct fanotify_event *fanotify_alloc_error_event(
 {
        struct fs_error_report *report =
                        fsnotify_data_error_report(data, data_type);
+       struct inode *inode;
        struct fanotify_error_event *fee;
+       int fh_len;
 
        if (WARN_ON_ONCE(!report))
                return NULL;
@@ -622,6 +624,15 @@ static struct fanotify_event *fanotify_alloc_error_event(
        fee->err_count = 1;
        fee->fsid = *fsid;
 
+       inode = report->inode;
+       fh_len = fanotify_encode_fh_len(inode);
+
+       /* Bad fh_len. Fallback to using an invalid fh. Should never happen. */
+       if (!fh_len && inode)
+               inode = NULL;
+
+       fanotify_encode_fh(&fee->object_fh, inode, fh_len, NULL, 0);
+
        *hash ^= fanotify_hash_fsid(fsid);
 
        return &fee->fae;

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 80af269..edd7587 100644 (file)
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -208,6 +208,8 @@ struct fanotify_error_event {
        u32 err_count; /* Suppressed errors count */
 
        __kernel_fsid_t fsid; /* FSID this error refers to. */
+
+       FANOTIFY_INLINE_FH(object_fh, MAX_HANDLE_SZ);
 };
 
 static inline struct fanotify_error_event *
@@ -222,6 +224,8 @@ static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
                return &FANOTIFY_FE(event)->fsid;
        else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
                return &FANOTIFY_NE(event)->fsid;
+       else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
+               return &FANOTIFY_EE(event)->fsid;
        else
                return NULL;
 }
@@ -233,6 +237,8 @@ static inline struct fanotify_fh *fanotify_event_object_fh(
                return &FANOTIFY_FE(event)->object_fh;
        else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
                return fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
+       else if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
+               return &FANOTIFY_EE(event)->object_fh;
        else
                return NULL;
 }
@@ -266,6 +272,9 @@ static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
 
 static inline bool fanotify_event_has_object_fh(struct fanotify_event *event)
 {
+       /* For error events, even zeroed fh are reported. */
+       if (event->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
+               return true;
        return fanotify_event_object_fh_len(event) > 0;
 }
 

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index a9b5c36..ff4a737 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -339,9 +339,6 @@ 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;
 
@@ -376,6 +373,11 @@ 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;