diff options
| author | Amir Goldstein <amir73il@gmail.com> | 2024-11-15 10:30:25 -0500 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2024-12-10 12:03:17 +0100 |
| commit | b4b2ff4f61ded819bfa22e50fdec7693f51cbbee (patch) | |
| tree | 967a77c693130977627fd981408ac8dd16d30c11 /include/uapi | |
| parent | fanotify: report file range info with pre-content events (diff) | |
| download | linux-b4b2ff4f61ded819bfa22e50fdec7693f51cbbee.tar.gz linux-b4b2ff4f61ded819bfa22e50fdec7693f51cbbee.zip | |
fanotify: allow to set errno in FAN_DENY permission response
With FAN_DENY response, user trying to perform the filesystem operation
gets an error with errno set to EPERM.
It is useful for hierarchical storage management (HSM) service to be able
to deny access for reasons more diverse than EPERM, for example EAGAIN,
if HSM could retry the operation later.
Allow fanotify groups with priority FAN_CLASSS_PRE_CONTENT to responsd
to permission events with the response value FAN_DENY_ERRNO(errno),
instead of FAN_DENY to return a custom error.
Limit custom error values to errors expected on read(2)/write(2) and
open(2) of regular files. This list could be extended in the future.
Userspace can test for legitimate values of FAN_DENY_ERRNO(errno) by
writing a response to an fanotify group fd with a value of FAN_NOFD in
the fd field of the response.
The change in fanotify_response is backward compatible, because errno is
written in the high 8 bits of the 32bit response field and old kernels
reject respose value with high bits set.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/1e5fb6af84b69ca96b5c849fa5f10bdf4d1dc414.1731684329.git.josef@toxicpanda.com
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/linux/fanotify.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h index 0636a9c85dd0..bd8167979707 100644 --- a/include/uapi/linux/fanotify.h +++ b/include/uapi/linux/fanotify.h @@ -235,6 +235,13 @@ struct fanotify_response_info_audit_rule { /* Legit userspace responses to a _PERM event */ #define FAN_ALLOW 0x01 #define FAN_DENY 0x02 +/* errno other than EPERM can specified in upper byte of deny response */ +#define FAN_ERRNO_BITS 8 +#define FAN_ERRNO_SHIFT (32 - FAN_ERRNO_BITS) +#define FAN_ERRNO_MASK ((1 << FAN_ERRNO_BITS) - 1) +#define FAN_DENY_ERRNO(err) \ + (FAN_DENY | ((((__u32)(err)) & FAN_ERRNO_MASK) << FAN_ERRNO_SHIFT)) + #define FAN_AUDIT 0x10 /* Bitmask to create audit record for result */ #define FAN_INFO 0x20 /* Bitmask to indicate additional information */ |