From: Ian Kent <raven@themaw.net>
To: David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: viro@zeniv.linux.org.uk, kzak@redhat.com, jlayton@redhat.com,
mszeredi@redhat.com, nicolas.dichtel@6wind.com,
christian@brauner.io, linux-api@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [GIT PULL] Mount notifications
Date: Tue, 04 Aug 2020 06:48:45 +0800 [thread overview]
Message-ID: <8eb2e52f1cbdbb8bcf5c5205a53bdc9aaa11a071.camel@themaw.net> (raw)
In-Reply-To: <1842689.1596468469@warthog.procyon.org.uk>
On Mon, 2020-08-03 at 16:27 +0100, David Howells wrote:
> Hi Linus,
>
> Here's a set of patches to add notifications for mount topology
> events,
> such as mounting, unmounting, mount expiry, mount reconfiguration.
>
> The first patch in the series adds a hard limit on the number of
> watches
> that any particular user can add. The RLIMIT_NOFILE value for the
> process
> adding a watch is used as the limit. Even if you don't take the rest
> of
> the series, can you at least take this one?
>
> An LSM hook is included for an LSM to rule on whether or not a mount
> watch
> may be set on a particular path.
>
> This series is intended to be taken in conjunction with the fsinfo
> series
> which I'll post a pull request for shortly and which is dependent on
> it.
>
> Karel Zak[*] has created preliminary patches that add support to
> libmount
> and Ian Kent has started working on making systemd use them.
>
> [*] https://github.com/karelzak/util-linux/commits/topic/fsinfo
>
> Note that there have been some last minute changes to the patchset:
> you
> wanted something adding and Miklós wanted some bits taking
> out/changing.
> I've placed a tag, fsinfo-core-20200724 on the aggregate of these two
> patchsets that can be compared to fsinfo-core-20200803.
>
> To summarise the changes: I added the limiter that you wanted;
> removed an
> unused symbol; made the mount ID fields in the notificaion 64-bit
> (the
> fsinfo patchset has a change to convey the mount uniquifier instead
> of the
> mount ID); removed the event counters from the mount notification and
> moved
> the event counters into the fsinfo patchset.
I've pushed my systemd changes to a github repo.
I haven't yet updated it with the changes above but will get to it.
They can be found at:
https://github.com/raven-au/systemd.git branch notifications-devel
>
>
> ====
> WHY?
> ====
>
> Why do we want mount notifications? Whilst /proc/mounts can be
> polled, it
> only tells you that something changed in your namespace. To find
> out, you
> have to trawl /proc/mounts or similar to work out what changed in the
> mount
> object attributes and mount topology. I'm told that the proc file
> holding
> the namespace_sem is a point of contention, especially as the process
> of
> generating the text descriptions of the mounts/superblocks can be
> quite
> involved.
>
> The notification generated here directly indicates the mounts
> involved in
> any particular event and gives an idea of what the change was.
>
> This is combined with a new fsinfo() system call that allows, amongst
> other
> things, the ability to retrieve in one go an { id, change_counter }
> tuple
> from all the children of a specified mount, allowing buffer overruns
> to be
> dealt with quickly.
>
> This is of use to systemd to improve efficiency:
>
>
> https://lore.kernel.org/linux-fsdevel/20200227151421.3u74ijhqt6ekbiss@ws.net.home/
>
> And it's not just Red Hat that's potentially interested in this:
>
>
> https://lore.kernel.org/linux-fsdevel/293c9bd3-f530-d75e-c353-ddeabac27cf6@6wind.com/
>
>
> David
> ---
> The following changes since commit
> ba47d845d715a010f7b51f6f89bae32845e6acb7:
>
> Linux 5.8-rc6 (2020-07-19 15:41:18 -0700)
>
> are available in the Git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
> tags/mount-notifications-20200803
>
> for you to fetch changes up to
> 841a0dfa511364fa9a8d67512e0643669f1f03e3:
>
> watch_queue: sample: Display mount tree change notifications (2020-
> 08-03 12:15:38 +0100)
>
> ----------------------------------------------------------------
> Mount notifications
>
> ----------------------------------------------------------------
> David Howells (5):
> watch_queue: Limit the number of watches a user can hold
> watch_queue: Make watch_sizeof() check record size
> watch_queue: Add security hooks to rule on setting mount
> watches
> watch_queue: Implement mount topology and attribute change
> notifications
> watch_queue: sample: Display mount tree change notifications
>
> Documentation/watch_queue.rst | 12 +-
> arch/alpha/kernel/syscalls/syscall.tbl | 1 +
> arch/arm/tools/syscall.tbl | 1 +
> arch/arm64/include/asm/unistd.h | 2 +-
> arch/arm64/include/asm/unistd32.h | 2 +
> 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 +
> fs/Kconfig | 9 ++
> fs/Makefile | 1 +
> fs/mount.h | 18 +++
> fs/mount_notify.c | 222
> ++++++++++++++++++++++++++++
> fs/namespace.c | 22 +++
> include/linux/dcache.h | 1 +
> include/linux/lsm_hook_defs.h | 3 +
> include/linux/lsm_hooks.h | 6 +
> include/linux/sched/user.h | 3 +
> include/linux/security.h | 8 +
> include/linux/syscalls.h | 2 +
> include/linux/watch_queue.h | 7 +-
> include/uapi/asm-generic/unistd.h | 4 +-
> include/uapi/linux/watch_queue.h | 31 +++-
> kernel/sys_ni.c | 3 +
> kernel/watch_queue.c | 8 +
> samples/watch_queue/watch_test.c | 41 ++++-
> security/security.c | 7 +
> 37 files changed, 422 insertions(+), 6 deletions(-)
> create mode 100644 fs/mount_notify.c
>
prev parent reply other threads:[~2020-08-03 22:48 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 15:27 [GIT PULL] Mount notifications David Howells
2020-08-03 15:49 ` [GIT PULL] Filesystem Information David Howells
2020-08-03 16:42 ` Miklos Szeredi
2020-08-04 2:15 ` Ian Kent
2020-08-04 14:36 ` Miklos Szeredi
2020-08-05 1:33 ` Ian Kent
2020-08-05 8:00 ` Miklos Szeredi
2020-08-05 11:13 ` Ian Kent
2020-08-05 8:24 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Miklos Szeredi
2020-08-11 13:54 ` Miklos Szeredi
2020-08-11 14:08 ` Al Viro
2020-08-11 14:22 ` Miklos Szeredi
2020-08-11 14:31 ` Al Viro
[not found] ` <CAAgocE07=vVKpQhG+rjEGO=NEBKZ02gjg4TRPxECAc+RKrzn=Q@mail.gmail.com>
2020-08-11 14:36 ` Al Viro
2020-08-11 14:36 ` Miklos Szeredi
2020-08-11 14:42 ` Al Viro
2020-08-11 14:47 ` Miklos Szeredi
2020-08-11 15:20 ` Linus Torvalds
2020-08-11 15:30 ` Miklos Szeredi
2020-08-11 16:05 ` Linus Torvalds
2020-08-11 18:49 ` Miklos Szeredi
2020-08-11 19:31 ` Lennart Poettering
2020-08-11 19:50 ` Christian Brauner
2020-08-11 19:39 ` Christian Brauner
2020-08-12 0:53 ` Ian Kent
2020-08-11 15:39 ` Andy Lutomirski
2020-08-11 16:17 ` Casey Schaufler
2020-08-11 16:30 ` Linus Torvalds
2020-08-11 20:28 ` Miklos Szeredi
2020-08-11 20:36 ` Jann Horn
2020-08-11 20:56 ` Miklos Szeredi
2020-08-11 21:17 ` Andy Lutomirski
2020-08-11 21:18 ` Linus Torvalds
2020-08-12 7:23 ` Miklos Szeredi
2020-08-12 14:39 ` Al Viro
2020-08-12 14:46 ` Miklos Szeredi
2020-08-12 15:08 ` Al Viro
2020-08-12 15:13 ` Miklos Szeredi
2020-08-12 16:33 ` Al Viro
2020-08-12 17:16 ` Miklos Szeredi
2020-08-12 17:39 ` Al Viro
2020-08-12 18:33 ` Al Viro
2020-08-12 21:30 ` Al Viro
2020-08-18 9:41 ` Miklos Szeredi
2020-08-18 9:30 ` Miklos Szeredi
2020-08-12 15:22 ` David Howells
2020-08-11 21:20 ` Al Viro
2020-08-11 21:35 ` Casey Schaufler
2020-08-11 16:05 ` Al Viro
2020-08-11 16:09 ` Linus Torvalds
2020-08-11 16:39 ` Al Viro
2020-08-12 10:14 ` Karel Zak
2020-08-12 13:09 ` Miklos Szeredi
2020-08-12 13:33 ` David Howells
2020-08-12 13:54 ` Miklos Szeredi
2020-08-12 0:05 ` David Howells
2020-08-12 7:55 ` Miklos Szeredi
2020-08-12 8:29 ` David Howells
2020-08-12 8:37 ` Miklos Szeredi
2020-08-12 9:43 ` file metadata via fs API Steven Whitehouse
2020-08-12 10:04 ` Miklos Szeredi
2020-08-12 11:28 ` Karel Zak
2020-08-12 12:43 ` Miklos Szeredi
2020-08-13 8:52 ` Karel Zak
2020-08-12 13:06 ` David Howells
2020-08-13 1:01 ` Ian Kent
2020-08-12 18:18 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Linus Torvalds
2020-08-12 19:34 ` file metadata via fs API Steven Whitehouse
2020-08-12 19:50 ` Linus Torvalds
2020-08-13 3:44 ` Ian Kent
2020-08-13 10:36 ` Karel Zak
2020-08-14 7:58 ` Lennart Poettering
2020-08-17 11:32 ` Steven Whitehouse
2020-08-17 17:15 ` Linus Torvalds
2020-08-17 22:44 ` Linus Torvalds
2020-08-18 12:50 ` Miklos Szeredi
2020-08-18 18:51 ` Linus Torvalds
2020-08-18 20:18 ` Miklos Szeredi
2020-08-18 20:53 ` Linus Torvalds
2020-08-21 13:17 ` Miklos Szeredi
2020-08-19 2:29 ` Al Viro
2020-08-13 3:53 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Jeffrey E Altman
2020-08-14 17:05 ` Linus Torvalds
2020-08-18 15:01 ` Jeffrey E Altman
2020-08-14 8:06 ` Lennart Poettering
2020-08-12 13:54 ` David Howells
2020-08-12 14:10 ` Miklos Szeredi
2020-08-12 14:23 ` David Howells
2020-08-03 22:48 ` Ian Kent [this message]
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