| Message ID | 1449138.1585578664@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [GIT,PULL] General notification queue and key notifications | expand |
Hi David, On Mon, 30 Mar 2020 15:31:04 +0100 David Howells <dhowells@redhat.com> wrote: > > pipe: Add general notification queue support This commit has a (reasonably simple) conflict against commit 6551d5c56eb0 ("pipe: make sure to wake up everybody when the last reader/writer closes") from Linus' tree. Also a semantic conflict against commit 52b31bc9aabc ("io_uring: add splice(2) support") from the block tree needing this fix up (white space damaged) diff --git a/fs/io_uring.c b/fs/io_uring.c index fb8fe0bd5e18..8cdd3870cd4e 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2470,7 +2470,7 @@ static int io_splice_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) static bool io_splice_punt(struct file *file) { - if (get_pipe_info(file)) + if (get_pipe_info(file, true)) return false; if (!io_file_supports_async(file)) return true; > security: Add hooks to rule on setting a watch > security: Add a hook for the point of notification insertion And these have a conflict against commitinclude/linux/lsm_hooks.h 98e828a0650f ("security: Refactor declaration of LSM hooks") from the bpf-next tree (will be in the net-next tree pull). That requires taking the net-next version of include/linux/lsm_hooks.h and then applying the following patch: diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 9cd4455528e5..4f8d63fd1327 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -252,6 +252,16 @@ LSM_HOOK(int, 0, inode_notifysecctx, struct inode *inode, void *ctx, u32 ctxlen) LSM_HOOK(int, 0, inode_setsecctx, struct dentry *dentry, void *ctx, u32 ctxlen) LSM_HOOK(int, 0, inode_getsecctx, struct inode *inode, void **ctx, u32 *ctxlen) +#ifdef CONFIG_KEY_NOTIFICATIONS +LSM_HOOK(int, 0, watch_key, struct key *key) +#endif +#ifdef CONFIG_DEVICE_NOTIFICATIONS +LSM_HOOK(int, 0, watch_devices, void) +#endif +#ifdef CONFIG_WATCH_QUEUE +LSM_HOOK(int, 0, post_notification, const struct cred *w_cred, + const struct cred *cred, struct watch_notification *n) +#endif #ifdef CONFIG_SECURITY_NETWORK LSM_HOOK(int, 0, unix_stream_connect, struct sock *sock, struct sock *other,
Hi Linus, Can you pull this, please? It adds a general notification queue concept and adds an event source for keys/keyrings, such as linking and unlinking keys and changing their attributes. A subsequent pull request will add mount and superblock event sources. 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 SELinux and Smack with implementations of some of these hooks. WHY === Key/keyring notifications are desirable because if you have your kerberos tickets in a file/directory, your Gnome desktop will monitor that using something like fanotify and tell you if your credentials cache changes. However, we also have the ability to cache your kerberos tickets in the session, user or persistent keyring so that it isn't left around on disk across a reboot or logout. Keyrings, however, cannot currently be monitored asynchronously, so the desktop has to poll for it - not so good on a laptop. This source will allow the desktop to avoid the need to poll. Here's a pull request for usage by gnome-online-accounts: https://gitlab.gnome.org/GNOME/gnome-online-accounts/merge_requests/47 DESIGN DECISIONS ================ (1) The notification queue is built on top of a standard pipe. Messages are effectively spliced in. The pipe is opened with a special flag: pipe2(fds, O_NOTIFICATION_PIPE); The special flag has the same value as O_EXCL (which doesn't seem like it will ever be applicable in this context)[?]. It is given up front to make it a lot easier to prohibit splice and co. from accessing the pipe. [?] Should this be done some other way? I'd rather not use up a new O_* flag if I can avoid it - should I add a pipe3() system call instead? The pipe is then configured:: ioctl(fds[1], IOC_WATCH_QUEUE_SET_SIZE, queue_depth); ioctl(fds[1], IOC_WATCH_QUEUE_SET_FILTER, &filter); Messages are then read out of the pipe using read(). (2) It should be possible to allow write() to insert data into the notification pipes too, but this is currently disabled as the kernel has to be able to insert messages into the pipe *without* holding pipe->mutex and the code to make this work needs careful auditing. (3) sendfile(), splice() and vmsplice() are disabled on notification pipes because of the pipe->mutex issue and also because they sometimes want to revert what they just did - but one or more notification messages might've been interleaved in the ring. (4) The kernel inserts messages with the wait queue spinlock held. This means that pipe_read() and pipe_write() have to take the spinlock to update the queue pointers. (5) Records in the buffer are binary, typed and have a length so that they can be of varying size. This allows multiple heterogeneous sources to share a common buffer; there are 16 million types available, of which I've used just a few, so there is scope for others to be used. Tags may be specified when a watchpoint is created to help distinguish the sources. (6) Records are filterable as types have up to 256 subtypes that can be individually filtered. Other filtration is also available. (7) Notification pipes don't interfere with each other; each may be bound to a different set of watches. Any particular notification will be copied to all the queues that are currently watching for it - and only those that are watching for it. (8) When recording a notification, the kernel will not sleep, but will rather mark a queue as having lost a message if there's insufficient space. read() will fabricate a loss notification message at an appropriate point later. (9) The notification pipe is created and then watchpoints are attached to it, using one of: keyctl_watch_key(KEY_SPEC_SESSION_KEYRING, fds[1], 0x01); watch_mount(AT_FDCWD, "/", 0, fd, 0x02); watch_sb(AT_FDCWD, "/mnt", 0, fd, 0x03); where in both cases, fd indicates the queue and the number after is a tag between 0 and 255. (10) Watches are removed if either the notification pipe is destroyed or the watched object is destroyed. In the latter case, a message will be generated indicating the enforced watch removal. 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. TESTING AND MANPAGES ==================== (*) The keyutils tree has a pipe-watch branch that has keyctl commands for making use of notifications. Proposed manual pages can also be found on this branch, though a couple of them really need to go to the main manpages repository instead. If the kernel supports the watching of keys, then running "make test" on that branch will cause the testing infrastructure to spawn a monitoring process on the side that monitors a notifications pipe for all the key/keyring changes induced by the tests and they'll all be checked off to make sure they happened. https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=pipe-watch (*) A test program is provided (samples/watch_queue/watch_test) that can be used to monitor for keyrings, mount and superblock events. Information on the notifications is simply logged to stdout. Thanks, David --- The following changes since commit f8788d86ab28f61f7b46eb6be375f8a726783636: Linux 5.6-rc3 (2020-02-23 16:17:42 -0800) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/notifications-20200330 for you to fetch changes up to 694435dbde3d1da79aafaf4cd680802f9eb229b7: smack: Implement the watch_key and post_notification hooks (2020-03-19 17:31:09 +0000) ---------------------------------------------------------------- Notifications over pipes ---------------------------------------------------------------- David Howells (11): uapi: General notification queue definitions security: Add hooks to rule on setting a watch security: Add a hook for the point of notification insertion pipe: Add O_NOTIFICATION_PIPE pipe: Add general notification queue support watch_queue: Add a key/keyring notification facility Add sample notification program pipe: Allow buffers to be marked read-whole-or-error for notifications pipe: Add notification lossage handling selinux: Implement the watch_key security hook smack: Implement the watch_key and post_notification hooks Documentation/security/keys/core.rst | 57 ++ Documentation/userspace-api/ioctl/ioctl-number.rst | 1 + Documentation/watch_queue.rst | 339 +++++++++++ fs/pipe.c | 242 +++++--- fs/splice.c | 12 +- include/linux/key.h | 3 + include/linux/lsm_audit.h | 1 + include/linux/lsm_hooks.h | 38 ++ include/linux/pipe_fs_i.h | 27 +- include/linux/security.h | 31 + include/linux/watch_queue.h | 127 ++++ include/uapi/linux/keyctl.h | 2 + include/uapi/linux/watch_queue.h | 104 ++++ init/Kconfig | 12 + kernel/Makefile | 1 + kernel/watch_queue.c | 659 +++++++++++++++++++++ samples/Kconfig | 6 + samples/Makefile | 1 + samples/watch_queue/Makefile | 7 + samples/watch_queue/watch_test.c | 186 ++++++ 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 | 83 ++- 31 files changed, 2079 insertions(+), 105 deletions(-) create mode 100644 Documentation/watch_queue.rst create mode 100644 include/linux/watch_queue.h create mode 100644 include/uapi/linux/watch_queue.h create mode 100644 kernel/watch_queue.c create mode 100644 samples/watch_queue/Makefile create mode 100644 samples/watch_queue/watch_test.c