From: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx> Document the limited fanotify functionality that will be available for unprivileged users from kernel v5.13. Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- man2/fanotify_init.2 | 77 +++++++++++++++++++++++++++++++++++++------- man2/fanotify_mark.2 | 9 ++++++ 2 files changed, 74 insertions(+), 12 deletions(-) diff --git a/man2/fanotify_init.2 b/man2/fanotify_init.2 index ff656f438..5f54a8506 100644 --- a/man2/fanotify_init.2 +++ b/man2/fanotify_init.2 @@ -57,15 +57,6 @@ In the current implementation, the number of fanotify groups per user is limited to 128. This limit cannot be overridden. .PP -Calling -.BR fanotify_init () -requires the -.B CAP_SYS_ADMIN -capability. -This constraint might be relaxed in future versions of the API. -Therefore, certain additional capability checks have been implemented as -indicated below. -.PP The .I flags argument contains a multi-bit field defining the notification class of the @@ -86,6 +77,9 @@ It is intended for event listeners that need to access files before they contain their final data. This notification class might be used by hierarchical storage managers, for example. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_CLASS_CONTENT This value allows the receipt of events notifying that a file has been @@ -94,6 +88,9 @@ It is intended for event listeners that need to access files when they already contain their final content. This notification class might be used by malware detection programs, for example. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_CLASS_NOTIF This is the default value. @@ -155,6 +152,9 @@ supplied to .BR read (2) (see .BR fanotify (7)). +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .BR FAN_ENABLE_AUDIT " (since Linux 4.15)" .\" commit de8cd83e91bc3ee212b3e6ec6e4283af9e4ab269 @@ -163,6 +163,9 @@ permission events. The permission event response has to be marked with the .B FAN_AUDIT flag for an audit log record to be generated. +Use of this flag requires the +.B CAP_AUDIT_WRITE +capability. .TP .BR FAN_REPORT_FID " (since Linux 5.1)" .\" commit a8b13aa20afb69161b5123b4f1acc7ea0a03d360 @@ -378,13 +381,63 @@ The fanotify API is available only if the kernel was configured with .BR CONFIG_FANOTIFY . .TP .B EPERM -The operation is not permitted because the caller lacks the -.B CAP_SYS_ADMIN -capability. +The operation is not permitted because the caller lacks a required capability. .SH VERSIONS .BR fanotify_init () was introduced in version 2.6.36 of the Linux kernel and enabled in version 2.6.37. +.PP +Prior to Linux 5.13, +.\" commit 7cea2a3c505e87a9d6afc78be4a7f7be636a73a7 +calling +.BR fanotify_init () +required the +.B CAP_SYS_ADMIN +capability. +Since Linux 5.13, +.\" commit 7cea2a3c505e87a9d6afc78be4a7f7be636a73a7 +users may call +.BR fanotify_init () +without the +.B CAP_SYS_ADMIN +capability to create and intialize an fanotify group with limited functionality. +.TP +The limitations imposed on an event listener created by a user without the +.B CAP_SYS_ADMIN +capability are as follows: +.RS +.IP * 3 +The user cannot request for an unlimited event queue by using +.BR FAN_UNLIMITED_QUEUE . +.IP * 3 +The user cannot request for an unlimited number of marks by using +.BR FAN_UNLIMITED_MARKS . +.IP * 3 +The user cannot request to use either notification classes +.BR FAN_CLASS_CONTENT +or +.BR FAN_CLASS_PRE_CONTENT . +This means that user cannot request permission events. +.IP * 3 +The user is required to create a group that identifies filesystem objects by +file handles, for example, by providing the +.BR FAN_REPORT_FID +flag. +.IP * 3 +The user is limited to only mark inodes. +The ability to mark a mount or filesystem via +.BR fanotify_mark() +through the use of +.BR FAN_MARK_MOUNT +or +.BR FAN_MARK_FILESYSTEM +is not permitted. +.IP * 3 +The event object in the event queue is limited in terms of the information +that is made available to the unprivileged user. +A user will also not receive the pid that generated the event, unless the +listening process itself generated the event. +.RE .SH CONFORMING TO This system call is Linux-specific. .SH BUGS diff --git a/man2/fanotify_mark.2 b/man2/fanotify_mark.2 index d5dcecc74..1bd0a30ea 100644 --- a/man2/fanotify_mark.2 +++ b/man2/fanotify_mark.2 @@ -142,6 +142,9 @@ contains Attempting to do so will result in the error .B EINVAL being returned. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .BR FAN_MARK_FILESYSTEM " (since Linux 4.20)" .\" commit d54f4fba889b205e9cd8239182ca5d27d0ac3bc2 @@ -152,6 +155,9 @@ The filesystem containing will be marked. All the contained files and directories of the filesystem from any mount point will be monitored. +Use of this flag requires the +.B CAP_SYS_ADMIN +capability. .TP .B FAN_MARK_IGNORED_MASK The events in @@ -441,6 +447,9 @@ handles. This error can be returned only with an fanotify group that identifies filesystem objects by file handles. .TP +.B EPERM +The operation is not permitted because the caller lacks a required capability. +.TP .B EXDEV The filesystem object indicated by .I pathname -- 2.25.1
