kernel/git/stable/linux.git/fs/tracefs/inode.c, branch linux-6.7.y

eventfs: Clean up dentry ops and add revalidate function

2024-02-23T08:51:44+00:00

commit 8dce06e98c70a7fcbb4bca7d90faf40522e65c58 upstream. In order for the dentries to stay up-to-date with the eventfs changes, just add a 'd_revalidate' function that checks the 'is_freed' bit. Also, clean up the dentry release to actually use d_release() rather than the slightly odd d_iput() function. We don't care about the inode, all we want to do is to get rid of the refcount to the eventfs data added by dentry->d_fsdata. It would probably be cleaner to make eventfs its own filesystem, or at least set its own dentry ops when looking up eventfs files. But as it is, only eventfs dentries use d_fsdata, so we don't really need to split these things up by use. Another thing that might be worth doing is to make all eventfs lookups mark their dentries as not worth caching. We could do that with d_delete(), but the DCACHE_DONTCACHE flag would likely be even better. As it is, the dentries are all freeable, but they only tend to get freed at memory pressure rather than more proactively. But that's a separate issue. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131185513.124644253@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Christian Brauner Cc: Al Viro Cc: Ajay Kaher Cc: Greg Kroah-Hartman Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman

tracefs: dentry lookup crapectomy

2024-02-23T08:51:44+00:00

commit 49304c2b93e4f7468b51ef717cbe637981397115 upstream. The dentry lookup for eventfs files was very broken, and had lots of signs of the old situation where the filesystem names were all created statically in the dentry tree, rather than being looked up dynamically based on the eventfs data structures. You could see it in the naming - how it claimed to "create" dentries rather than just look up the dentries that were given it. You could see it in various nonsensical and very incorrect operations, like using "simple_lookup()" on the dentries that were passed in, which only results in those dentries becoming negative dentries. Which meant that any other lookup would possibly return ENOENT if it saw that negative dentry before the data was then later filled in. You could see it in the immense amount of nonsensical code that didn't actually just do lookups. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131233227.73db55e1@gandalf.local.home Cc: stable@vger.kernel.org Cc: Al Viro Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Christian Brauner Cc: Greg Kroah-Hartman Cc: Ajay Kaher Cc: Mark Rutland Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman

tracefs: Zero out the tracefs_inode when allocating it

2024-02-23T08:51:44+00:00

commit d81786f53aec14fd4d56263145a0635afbc64617 upstream. eventfs uses the tracefs_inode and assumes that it's already initialized to zero. That is, it doesn't set fields to zero (like ti->private) after getting its tracefs_inode. This causes bugs due to stale values. Just initialize the entire structure to zero on allocation so there isn't any more surprises. This is a partial fix to access to ti->private. The assignment still needs to be made before the dentry is instantiated. Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.315825944@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Christian Brauner Cc: Al Viro Cc: Ajay Kaher Cc: Greg Kroah-Hartman Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman

tracefs/eventfs: Use root and instance inodes as default ownership

2024-02-05T20:17:05+00:00

[ Upstream commit 8186fff7ab649085e2c60d032d9a20a85af1d87c ] Instead of walking the dentries on mount/remount to update the gid values of all the dentries if a gid option is specified on mount, just update the root inode. Add .getattr, .setattr, and .permissions on the tracefs inode operations to update the permissions of the files and directories. For all files and directories in the top level instance: /sys/kernel/tracing/* It will use the root inode as the default permissions. The inode that represents: /sys/kernel/tracing (or wherever it is mounted). When an instance is created: mkdir /sys/kernel/tracing/instance/foo The directory "foo" and all its files and directories underneath will use the default of what foo is when it was created. A remount of tracefs will not affect it. If a user were to modify the permissions of any file or directory in tracefs, it will also no longer be modified by a change in ownership of a remount. The events directory, if it is in the top level instance, will use the tracefs root inode as the default ownership for itself and all the files and directories below it. For the events directory in an instance ("foo"), it will keep the ownership of what it was when it was created, and that will be used as the default ownership for the files and directories beneath it. Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wjVdGkjDXBbvLn2wbZnqP4UsH46E3gqJ9m7UG6DpX2+WA@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240103215016.1e0c9811@gandalf.local.home Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Linus Torvalds Cc: Al Viro Cc: Christian Brauner Cc: Greg Kroah-Hartman Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin

tracefs: Check for dentry->d_inode exists in set_gid()

2024-01-02T20:20:22+00:00

If a getdents() is called on the tracefs directory but does not get all the files, it can leave a "cursor" dentry in the d_subdirs list of tracefs dentry. This cursor dentry does not have a d_inode for it. Before referencing tracefs_inode from the dentry, the d_inode must first be checked if it has content. If not, then it's not a tracefs_inode and can be ignored. The following caused a crash: #define getdents64(fd, dirp, count) syscall(SYS_getdents64, fd, dirp, count) #define BUF_SIZE 256 #define TDIR "/tmp/file0" int main(void) { char buf[BUF_SIZE]; int fd; int n; mkdir(TDIR, 0777); mount(NULL, TDIR, "tracefs", 0, NULL); fd = openat(AT_FDCWD, TDIR, O_RDONLY); n = getdents64(fd, buf, BUF_SIZE); ret = mount(NULL, TDIR, NULL, MS_NOSUID|MS_REMOUNT|MS_RELATIME|MS_LAZYTIME, "gid=1000"); return 0; } That's because the 256 BUF_SIZE was not big enough to read all the dentries of the tracefs file system and it left a "cursor" dentry in the subdirs of the tracefs root inode. Then on remounting with "gid=1000", it would cause an iteration of all dentries which hit: ti = get_tracefs(dentry->d_inode); if (ti && (ti->flags & TRACEFS_EVENT_INODE)) eventfs_update_gid(dentry, gid); Which crashed because of the dereference of the cursor dentry which had a NULL d_inode. In the subdir loop of the dentry lookup of set_gid(), if a child has a NULL d_inode, simply skip it. Link: https://lore.kernel.org/all/20240102135637.3a21fb10@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240102151249.05da244d@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Fixes: 7e8358edf503e ("eventfs: Fix file and directory uid and gid ownership") Reported-by: "Ubisectech Sirius" Signed-off-by: Steven Rostedt (Google)

eventfs: Fix file and directory uid and gid ownership

2023-12-22T13:13:55+00:00

It was reported that when mounting the tracefs file system with a gid other than root, the ownership did not carry down to the eventfs directory due to the dynamic nature of it. A fix was done to solve this, but it had two issues. (a) if the attr passed into update_inode_attr() was NULL, it didn't do anything. This is true for files that have not had a chown or chgrp done to itself or any of its sibling files, as the attr is allocated for all children when any one needs it. # umount /sys/kernel/tracing # mount -o rw,seclabel,relatime,gid=1000 -t tracefs nodev /mnt # ls -ld /mnt/events/sched drwxr-xr-x 28 root rostedt 0 Dec 21 13:12 /mnt/events/sched/ # ls -ld /mnt/events/sched/sched_switch drwxr-xr-x 2 root rostedt 0 Dec 21 13:12 /mnt/events/sched/sched_switch/ But when checking the files: # ls -l /mnt/events/sched/sched_switch total 0 -rw-r----- 1 root root 0 Dec 21 13:12 enable -rw-r----- 1 root root 0 Dec 21 13:12 filter -r--r----- 1 root root 0 Dec 21 13:12 format -r--r----- 1 root root 0 Dec 21 13:12 hist -r--r----- 1 root root 0 Dec 21 13:12 id -rw-r----- 1 root root 0 Dec 21 13:12 trigger (b) When the attr does not denote the UID or GID, it defaulted to using the parent uid or gid. This is incorrect as changing the parent uid or gid will automatically change all its children. # chgrp tracing /mnt/events/timer # ls -ld /mnt/events/timer drwxr-xr-x 2 root tracing 0 Dec 21 14:34 /mnt/events/timer # ls -l /mnt/events/timer total 0 -rw-r----- 1 root root 0 Dec 21 14:35 enable -rw-r----- 1 root root 0 Dec 21 14:35 filter drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_start drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_expire drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_state drwxr-xr-x 2 root tracing 0 Dec 21 14:35 tick_stop drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_start At first it was thought that this could be easily fixed by just making the default ownership of the superblock when it was mounted. But this does not handle the case of: # chgrp tracing instances # mkdir instances/foo If the superblock was used, then the group ownership would be that of what it was when it was mounted, when it should instead be "tracing". Instead, set a flag for the top level eventfs directory ("events") to flag which eventfs_inode belongs to it. Since the "events" directory's dentry and inode are never freed, it does not need to use its attr field to restore its mode and ownership. Use the this eventfs_inode's attr as the default ownership for all the files and directories underneath it. When the events eventfs_inode is created, it sets its ownership to its parent uid and gid. As the events directory is created at boot up before it gets mounted, this will always be uid=0 and gid=0. If it's created via an instance, then it will take the ownership of the instance directory. When the file system is mounted, it will update all the gids if one is specified. This will have a callback to update the events evenfs_inode's default entries. When a file or directory is created under the events directory, it will walk the ei->dentry parents until it finds the evenfs_inode that belongs to the events directory to retrieve the default uid and gid values. Link: https://lore.kernel.org/all/CAHk-=wiwQtUHvzwyZucDq8=Gtw+AnwScyLhpFswrQ84PjhoGsg@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231221190757.7eddbca9@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Dongliang Cui Cc: Hongyu Jin Fixes: 0dfc852b6fe3 ("eventfs: Have event files and directories default to parent uid and gid") Reviewed-by: Masami Hiramatsu (Google) Tested-by: Masami Hiramatsu (Google) Reported-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google)

eventfs: Do not allow NULL parent to eventfs_start_creating()

2023-11-22T23:37:26+00:00

The eventfs directory is dynamically created via the meta data supplied by the existing trace events. All files and directories in eventfs has a parent. Do not allow NULL to be passed into eventfs_start_creating() as the parent because that should never happen. Warn if it does. Link: https://lkml.kernel.org/r/20231121231112.693841807@goodmis.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Andrew Morton Reviewed-by: Josef Bacik Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2023-11-03T17:41:18+00:00

Pull tracing updates from Steven Rostedt: - Remove eventfs_file descriptor This is the biggest change, and the second part of making eventfs create its files dynamically. In 6.6 the first part was added, and that maintained a one to one mapping between eventfs meta descriptors and the directories and file inodes and dentries that were dynamically created. The directories were represented by a eventfs_inode and the files were represented by a eventfs_file. In v6.7 the eventfs_file is removed. As all events have the same directory make up (sched_switch has an "enable", "id", "format", etc files), the handing of what files are underneath each leaf eventfs directory is moved back to the tracing subsystem via a callback. When an event is added to the eventfs, it registers an array of evenfs_entry's. These hold the names of the files and the callbacks to call when the file is referenced. The callback gets the name so that the same callback may be used by multiple files. The callback then supplies the filesystem_operations structure needed to create this file. This has brought the memory footprint of creating multiple eventfs instances down by 2 megs each! - User events now has persistent events that are not associated to a single processes. These are privileged events that hang around even if no process is attached to them - Clean up of seq_buf There's talk about using seq_buf more to replace strscpy() and friends. But this also requires some minor modifications of seq_buf to be able to do this - Expand instance ring buffers individually Currently if boot up creates an instance, and a trace event is enabled on that instance, the ring buffer for that instance and the top level ring buffer are expanded (1.4 MB per CPU). This wastes memory as this happens when nothing is using the top level instance - Other minor clean ups and fixes * tag 'trace-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (34 commits) seq_buf: Export seq_buf_puts() seq_buf: Export seq_buf_putc() eventfs: Use simple_recursive_removal() to clean up dentries eventfs: Remove special processing of dput() of events directory eventfs: Delete eventfs_inode when the last dentry is freed eventfs: Hold eventfs_mutex when calling callback functions eventfs: Save ownership and mode eventfs: Test for ei->is_freed when accessing ei->dentry eventfs: Have a free_ei() that just frees the eventfs_inode eventfs: Remove "is_freed" union with rcu head eventfs: Fix kerneldoc of eventfs_remove_rec() tracing: Have the user copy of synthetic event address use correct context eventfs: Remove extra dget() in eventfs_create_events_dir() tracing: Have trace_event_file have ref counters seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str() eventfs: Fix typo in eventfs_inode union comment eventfs: Fix WARN_ON() in create_file_dentry() powerpc: Remove initialisation of readpos tracing/histograms: Simplify last_cmd_set() seq_buf: fix a misleading comment ...

tracefs: convert to new timestamp accessors

2023-10-18T12:08:28+00:00

Convert to using the new inode timestamp accessor functions. Signed-off-by: Jeff Layton Link: https://lore.kernel.org/r/20231004185347.80880-70-jlayton@kernel.org Signed-off-by: Christian Brauner

eventfs: Remove eventfs_file and just use eventfs_inode

2023-10-04T21:11:50+00:00

Instead of having a descriptor for every file represented in the eventfs directory, only have the directory itself represented. Change the API to send in a list of entries that represent all the files in the directory (but not other directories). The entry list contains a name and a callback function that will be used to create the files when they are accessed. struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent, const struct eventfs_entry *entries, int size, void *data); is used for the top level eventfs directory, and returns an eventfs_inode that will be used by: struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent, const struct eventfs_entry *entries, int size, void *data); where both of the above take an array of struct eventfs_entry entries for every file that is in the directory. The entries are defined by: typedef int (*eventfs_callback)(const char *name, umode_t *mode, void **data, const struct file_operations **fops); struct eventfs_entry { const char *name; eventfs_callback callback; }; Where the name is the name of the file and the callback gets called when the file is being created. The callback passes in the name (in case the same callback is used for multiple files), a pointer to the mode, data and fops. The data will be pointing to the data that was passed in eventfs_create_dir() or eventfs_create_events_dir() but may be overridden to point to something else, as it will be used to point to the inode->i_private that is created. The information passed back from the callback is used to create the dentry/inode. If the callback fills the data and the file should be created, it must return a positive number. On zero or negative, the file is ignored. This logic may also be used as a prototype to convert entire pseudo file systems into just-in-time allocation. The "show_events_dentry" file has been updated to show the directories, and any files they have. With just the eventfs_file allocations: Before after deltas for meminfo (in kB): MemFree: -14360 MemAvailable: -14260 Buffers: 40 Cached: 24 Active: 44 Inactive: 48 Inactive(anon): 28 Active(file): 44 Inactive(file): 20 Dirty: -4 AnonPages: 28 Mapped: 4 KReclaimable: 132 Slab: 1604 SReclaimable: 132 SUnreclaim: 1472 Committed_AS: 12 Before after deltas for slabinfo: : [ * = ] ext4_inode_cache 27 [* 1184 = 31968 ] extent_status 102 [* 40 = 4080 ] tracefs_inode_cache 144 [* 656 = 94464 ] buffer_head 39 [* 104 = 4056 ] shmem_inode_cache 49 [* 800 = 39200 ] filp -53 [* 256 = -13568 ] dentry 251 [* 192 = 48192 ] lsm_file_cache 277 [* 32 = 8864 ] vm_area_struct -14 [* 184 = -2576 ] trace_event_file 1748 [* 88 = 153824 ] kmalloc-1k 35 [* 1024 = 35840 ] kmalloc-256 49 [* 256 = 12544 ] kmalloc-192 -28 [* 192 = -5376 ] kmalloc-128 -30 [* 128 = -3840 ] kmalloc-96 10581 [* 96 = 1015776 ] kmalloc-64 3056 [* 64 = 195584 ] kmalloc-32 1291 [* 32 = 41312 ] kmalloc-16 2310 [* 16 = 36960 ] kmalloc-8 9216 [* 8 = 73728 ] Free memory dropped by 14,360 kB Available memory dropped by 14,260 kB Total slab additions in size: 1,771,032 bytes With this change: Before after deltas for meminfo (in kB): MemFree: -12084 MemAvailable: -11976 Buffers: 32 Cached: 32 Active: 72 Inactive: 168 Inactive(anon): 176 Active(file): 72 Inactive(file): -8 Dirty: 24 AnonPages: 196 Mapped: 8 KReclaimable: 148 Slab: 836 SReclaimable: 148 SUnreclaim: 688 Committed_AS: 324 Before after deltas for slabinfo: : [ * = ] tracefs_inode_cache 144 [* 656 = 94464 ] shmem_inode_cache -23 [* 800 = -18400 ] filp -92 [* 256 = -23552 ] dentry 179 [* 192 = 34368 ] lsm_file_cache -3 [* 32 = -96 ] vm_area_struct -13 [* 184 = -2392 ] trace_event_file 1748 [* 88 = 153824 ] kmalloc-1k -49 [* 1024 = -50176 ] kmalloc-256 -27 [* 256 = -6912 ] kmalloc-128 1864 [* 128 = 238592 ] kmalloc-64 4685 [* 64 = 299840 ] kmalloc-32 -72 [* 32 = -2304 ] kmalloc-16 256 [* 16 = 4096 ] total = 721352 Free memory dropped by 12,084 kB Available memory dropped by 11,976 kB Total slab additions in size: 721,352 bytes That's over 2 MB in savings per instance for free and available memory, and over 1 MB in savings per instance of slab memory. Link: https://lore.kernel.org/linux-trace-kernel/20231003184059.4924468e@gandalf.local.home Link: https://lore.kernel.org/linux-trace-kernel/20231004165007.43d79161@gandalf.local.home Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Andrew Morton Cc: Ajay Kaher Signed-off-by: Steven Rostedt (Google)