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    SubjectRe: [PATCH 00/11] Keyrings, Block and USB notifications [ver #7]
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    On 8/30/2019 6:57 AM, David Howells wrote:
    > Here's a set of patches to add a general notification queue concept and to
    > add sources of events for:
    >
    > (1) Key/keyring events, such as creating, linking and removal of keys.
    >
    > (2) General device events (single common queue) including:
    >
    > - Block layer events, such as device errors
    >
    > - USB subsystem events, such as device/bus attach/remove, device
    > reset, device errors.
    >
    > Tests for the key/keyring events can be found on the keyutils next branch:
    >
    > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=next

    I'm having trouble with the "make install" on Fedora. Is there an
    unusual dependency?

    >
    > Notifications are done automatically inside of the testing infrastructure
    > on every change to that every test makes to a key or keyring.
    >
    > Manual pages can be found there also, including pages for watch_queue(7)
    > and the watch_devices(2) system call (these should be transferred to the
    > manpages package if taken upstream).
    >
    > LSM hooks are included:
    >
    > (1) A set of hooks are provided that allow an LSM to rule on whether or
    > not a watch may be set. Each of these hooks takes a different
    > "watched object" parameter, so they're not really shareable. The LSM
    > should use current's credentials. [Wanted by SELinux & Smack]
    >
    > (2) A hook is provided to allow an LSM to rule on whether or not a
    > particular message may be posted to a particular queue. This is given
    > the credentials from the event generator (which may be the system) and
    > the watch setter. [Wanted by Smack]
    >
    > I've provided a preliminary attempt to provide SELinux and Smack with
    > implementations of some of these hooks.
    >
    >
    > Design decisions:
    >
    > (1) A misc chardev is used to create and open a ring buffer:
    >
    > fd = open("/dev/watch_queue", O_RDWR);
    >
    > which is then configured and mmap'd into userspace:
    >
    > ioctl(fd, IOC_WATCH_QUEUE_SET_SIZE, BUF_SIZE);
    > ioctl(fd, IOC_WATCH_QUEUE_SET_FILTER, &filter);
    > buf = mmap(NULL, BUF_SIZE * page_size, PROT_READ | PROT_WRITE,
    > MAP_SHARED, fd, 0);
    >
    > The fd cannot be read or written (though there is a facility to use
    > write to inject records for debugging) and userspace just pulls data
    > directly out of the buffer.
    >
    > (2) The ring index pointers are stored inside the ring and are thus
    > accessible to userspace. Userspace should only update the tail
    > pointer and never the head pointer or risk breaking the buffer. The
    > kernel checks that the pointers appear valid before trying to use
    > them. A 'skip' record is maintained around the pointers.
    >
    > (3) poll() can be used to wait for data to appear in the buffer.
    >
    > (4) Records in the buffer are binary, typed and have a length so that they
    > can be of varying size.
    >
    > This means that multiple heterogeneous sources can share a common
    > buffer. Tags may be specified when a watchpoint is created to help
    > distinguish the sources.
    >
    > (5) The queue is reusable as there are 16 million types available, of
    > which I've used just a few, so there is scope for others to be used.
    >
    > (6) Records are filterable as types have up to 256 subtypes that can be
    > individually filtered. Other filtration is also available.
    >
    > (7) Each time the buffer is opened, a new buffer is created - this means
    > that there's no interference between watchers.
    >
    > (8) When recording a notification, the kernel will not sleep, but will
    > rather mark a queue as overrun if there's insufficient space, thereby
    > avoiding userspace causing the kernel to hang.
    >
    > (9) The 'watchpoint' should be specific where possible, meaning that you
    > specify the object that you want to watch.
    >
    > (10) The buffer is created and then watchpoints are attached to it, using
    > one of:
    >
    > keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fd, 0x01);
    > watch_devices(fd, 0x02, 0);
    >
    > where in both cases, fd indicates the queue and the number after is a
    > tag between 0 and 255.
    >
    > (11) The watch must be removed if either the watch buffer is destroyed or
    > the watched object is destroyed.
    >
    >
    > Things I want to avoid:
    >
    > (1) Introducing features that make the core VFS dependent on the network
    > stack or networking namespaces (ie. usage of netlink).
    >
    > (2) Dumping all this stuff into dmesg and having a daemon that sits there
    > parsing the output and distributing it as this then puts the
    > responsibility for security into userspace and makes handling
    > namespaces tricky. Further, dmesg might not exist or might be
    > inaccessible inside a container.
    >
    > (3) Letting users see events they shouldn't be able to see.
    >
    >
    > The patches can be found here also:
    >
    > http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=notifications-core
    >
    > Changes:
    >
    > ver #7:
    >
    > (*) Removed the 'watch' argument from the security_watch_key() and
    > security_watch_devices() hooks as current_cred() can be used instead
    > of watch->cred.
    >
    > ver #6:
    >
    > (*) Fix mmap bug in watch_queue driver.
    >
    > (*) Add an extended removal notification that can transmit an identifier
    > to userspace (such as a key ID).
    >
    > (*) Don't produce a instantiation notification in mark_key_instantiated()
    > but rather do it in the caller to prevent key updates from producing
    > an instantiate notification as well as an update notification.
    >
    > (*) Set the right number of filters in the sample program.
    >
    > (*) Provide preliminary hook implementations for SELinux and Smack.
    >
    > ver #5:
    >
    > (*) Split the superblock watch and mount watch parts out into their own
    > branch (notifications-mount) as they really need certain fsinfo()
    > attributes.
    >
    > (*) Rearrange the watch notification UAPI header to push the length down
    > to bits 0-5 and remove the lost-message bits. The userspace's watch
    > ID tag is moved to bits 8-15 and then the message type is allocated
    > all of bits 16-31 for its own purposes.
    >
    > The lost-message bit is moved over to the header, rather than being
    > placed in the next message to be generated and given its own word so
    > it can be cleared with xchg(,0) for parisc.
    >
    > (*) The security_post_notification() hook is no longer called with the
    > spinlock held and softirqs disabled - though the RCU readlock is still
    > held.
    >
    > (*) Buffer pages are now accounted towards RLIMIT_MEMLOCK and CAP_IPC_LOCK
    > will skip the overuse check.
    >
    > (*) The buffer is marked VM_DONTEXPAND.
    >
    > (*) Save the watch-setter's creds in struct watch and give that to the LSM
    > hook for posting a message.
    >
    > ver #4:
    >
    > (*) Split the basic UAPI bits out into their own patch and then split the
    > LSM hooks out into an intermediate patch. Add LSM hooks for setting
    > watches.
    >
    > Rename the *_notify() system calls to watch_*() for consistency.
    >
    > ver #3:
    >
    > (*) I've added a USB notification source and reformulated the block
    > notification source so that there's now a common watch list, for which
    > the system call is now device_notify().
    >
    > I've assigned a pair of unused ioctl numbers in the 'W' series to the
    > ioctls added by this series.
    >
    > I've also added a description of the kernel API to the documentation.
    >
    > ver #2:
    >
    > (*) I've fixed various issues raised by Jann Horn and GregKH and moved to
    > krefs for refcounting. I've added some security features to try and
    > give Casey Schaufler the LSM control he wants.
    >
    > David
    > ---
    > David Howells (11):
    > uapi: General notification ring definitions
    > security: Add hooks to rule on setting a watch
    > security: Add a hook for the point of notification insertion
    > General notification queue with user mmap()'able ring buffer
    > keys: Add a notification facility
    > Add a general, global device notification watch list
    > block: Add block layer notifications
    > usb: Add USB subsystem notifications
    > Add sample notification program
    > selinux: Implement the watch_key security hook
    > smack: Implement the watch_key and post_notification hooks [untested]
    >
    >
    > Documentation/ioctl/ioctl-number.rst | 1
    > Documentation/security/keys/core.rst | 58 ++
    > Documentation/watch_queue.rst | 460 ++++++++++++++
    > arch/alpha/kernel/syscalls/syscall.tbl | 1
    > arch/arm/tools/syscall.tbl | 1
    > arch/ia64/kernel/syscalls/syscall.tbl | 1
    > arch/m68k/kernel/syscalls/syscall.tbl | 1
    > arch/microblaze/kernel/syscalls/syscall.tbl | 1
    > arch/mips/kernel/syscalls/syscall_n32.tbl | 1
    > arch/mips/kernel/syscalls/syscall_n64.tbl | 1
    > arch/mips/kernel/syscalls/syscall_o32.tbl | 1
    > arch/parisc/kernel/syscalls/syscall.tbl | 1
    > arch/powerpc/kernel/syscalls/syscall.tbl | 1
    > arch/s390/kernel/syscalls/syscall.tbl | 1
    > arch/sh/kernel/syscalls/syscall.tbl | 1
    > arch/sparc/kernel/syscalls/syscall.tbl | 1
    > arch/x86/entry/syscalls/syscall_32.tbl | 1
    > arch/x86/entry/syscalls/syscall_64.tbl | 1
    > arch/xtensa/kernel/syscalls/syscall.tbl | 1
    > block/Kconfig | 9
    > block/blk-core.c | 29 +
    > drivers/base/Kconfig | 9
    > drivers/base/Makefile | 1
    > drivers/base/watch.c | 90 +++
    > drivers/misc/Kconfig | 13
    > drivers/misc/Makefile | 1
    > drivers/misc/watch_queue.c | 893 +++++++++++++++++++++++++++
    > drivers/usb/core/Kconfig | 9
    > drivers/usb/core/devio.c | 56 ++
    > drivers/usb/core/hub.c | 4
    > include/linux/blkdev.h | 15
    > include/linux/device.h | 7
    > include/linux/key.h | 3
    > include/linux/lsm_audit.h | 1
    > include/linux/lsm_hooks.h | 38 +
    > include/linux/security.h | 32 +
    > include/linux/syscalls.h | 1
    > include/linux/usb.h | 18 +
    > include/linux/watch_queue.h | 94 +++
    > include/uapi/asm-generic/unistd.h | 4
    > include/uapi/linux/keyctl.h | 2
    > include/uapi/linux/watch_queue.h | 183 ++++++
    > kernel/sys_ni.c | 1
    > samples/Kconfig | 6
    > samples/Makefile | 1
    > samples/watch_queue/Makefile | 8
    > samples/watch_queue/watch_test.c | 233 +++++++
    > security/keys/Kconfig | 9
    > security/keys/compat.c | 3
    > security/keys/gc.c | 5
    > security/keys/internal.h | 30 +
    > security/keys/key.c | 38 +
    > security/keys/keyctl.c | 99 +++
    > security/keys/keyring.c | 20 -
    > security/keys/request_key.c | 4
    > security/security.c | 23 +
    > security/selinux/hooks.c | 14
    > security/smack/smack_lsm.c | 82 ++
    > 58 files changed, 2593 insertions(+), 30 deletions(-)
    > create mode 100644 Documentation/watch_queue.rst
    > create mode 100644 drivers/base/watch.c
    > create mode 100644 drivers/misc/watch_queue.c
    > create mode 100644 include/linux/watch_queue.h
    > create mode 100644 include/uapi/linux/watch_queue.h
    > create mode 100644 samples/watch_queue/Makefile
    > create mode 100644 samples/watch_queue/watch_test.c
    >

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