linux-ext4 - [PATCH v8 27/32] fanotify: Report fid info for file related file system errors

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Date:   Mon, 18 Oct 2021 21:00:10 -0300
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     jack@...e.com, amir73il@...il.com
Cc:     djwong@...nel.org, tytso@....edu, david@...morbit.com,
        dhowells@...hat.com, khazhy@...gle.com,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-api@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH v8 27/32] 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.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>

---
Changes since v7:
  - Move WARN_ON to separate patch (Amir)
  - Avoid duplication in the structure definition (Amir)
Changes since v6:
  - pass fsid from handle_events
Changes since v5:
  - Use preallocated MAX_HANDLE_SZ FH buffer
  - Report superblock errors with a zerolength INVALID FID (jan, amir)
---
 fs/notify/fanotify/fanotify.c | 10 ++++++++++
 fs/notify/fanotify/fanotify.h | 11 +++++++++++
 2 files changed, 21 insertions(+)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 45df610debbe..335ce8f88eb8 100644
--- 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 = report->inode;
 	struct fanotify_error_event *fee;
+	int fh_len;
 
 	if (WARN_ON_ONCE(!report))
 		return NULL;
@@ -622,6 +624,14 @@ static struct fanotify_event *fanotify_alloc_error_event(
 	fee->err_count = 1;
 	fee->fsid = *fsid;
 
+	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 bdf01ad4f9bf..4246a34667b5 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -209,6 +209,9 @@ struct fanotify_error_event {
 	u32 err_count; /* Suppressed errors count */
 
 	__kernel_fsid_t fsid; /* FSID this error refers to. */
+
+	/* This must be the last element of the structure. */
+	FANOTIFY_INLINE_FH(MAX_HANDLE_SZ);
 };
 
 static inline struct fanotify_error_event *
@@ -223,6 +226,8 @@ 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;
 }
@@ -234,6 +239,8 @@ 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;
 }
@@ -267,6 +274,10 @@ 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;
 	if (fanotify_event_object_fh_len(event) > 0)
 		return true;
 
-- 
2.33.0