kernel/linux.git/fs/proc/fd.c, branch v6.6.132

proc: Move fdinfo PTRACE_MODE_READ check into the inode .permission operation

2024-06-16T11:47:33+00:00

commit 0a960ba49869ebe8ff859d000351504dd6b93b68 upstream. The following commits loosened the permissions of /proc//fdinfo/ directory, as well as the files within it, from 0500 to 0555 while also introducing a PTRACE_MODE_READ check between the current task and 's task: - commit 7bc3fa0172a4 ("procfs: allow reading fdinfo with PTRACE_MODE_READ") - commit 1927e498aee1 ("procfs: prevent unprivileged processes accessing fdinfo dir") Before those changes, inode based system calls like inotify_add_watch(2) would fail when the current task didn't have sufficient read permissions: [...] lstat("/proc/1/task/1/fdinfo", {st_mode=S_IFDIR|0500, st_size=0, ...}) = 0 inotify_add_watch(64, "/proc/1/task/1/fdinfo", IN_MODIFY|IN_ATTRIB|IN_MOVED_FROM|IN_MOVED_TO|IN_CREATE|IN_DELETE| IN_ONLYDIR|IN_DONT_FOLLOW|IN_EXCL_UNLINK) = -1 EACCES (Permission denied) [...] This matches the documented behavior in the inotify_add_watch(2) man page: ERRORS EACCES Read access to the given file is not permitted. After those changes, inotify_add_watch(2) started succeeding despite the current task not having PTRACE_MODE_READ privileges on the target task: [...] lstat("/proc/1/task/1/fdinfo", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0 inotify_add_watch(64, "/proc/1/task/1/fdinfo", IN_MODIFY|IN_ATTRIB|IN_MOVED_FROM|IN_MOVED_TO|IN_CREATE|IN_DELETE| IN_ONLYDIR|IN_DONT_FOLLOW|IN_EXCL_UNLINK) = 1757 openat(AT_FDCWD, "/proc/1/task/1/fdinfo", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = -1 EACCES (Permission denied) [...] This change in behavior broke .NET prior to v7. See the github link below for the v7 commit that inadvertently/quietly (?) fixed .NET after the kernel changes mentioned above. Return to the old behavior by moving the PTRACE_MODE_READ check out of the file .open operation and into the inode .permission operation: [...] lstat("/proc/1/task/1/fdinfo", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0 inotify_add_watch(64, "/proc/1/task/1/fdinfo", IN_MODIFY|IN_ATTRIB|IN_MOVED_FROM|IN_MOVED_TO|IN_CREATE|IN_DELETE| IN_ONLYDIR|IN_DONT_FOLLOW|IN_EXCL_UNLINK) = -1 EACCES (Permission denied) [...] Reported-by: Kevin Parsons (Microsoft) Link: https://github.com/dotnet/runtime/commit/89e5469ac591b82d38510fe7de98346cce74ad4f Link: https://stackoverflow.com/questions/75379065/start-self-contained-net6-build-exe-as-service-on-raspbian-system-unauthorizeda Fixes: 7bc3fa0172a4 ("procfs: allow reading fdinfo with PTRACE_MODE_READ") Cc: stable@vger.kernel.org Cc: Christian Brauner Cc: Christian König Cc: Jann Horn Cc: Kalesh Singh Cc: Hardik Garg Cc: Allen Pais Signed-off-by: Tyler Hicks (Microsoft) Link: https://lore.kernel.org/r/20240501005646.745089-1-code@tyhicks.com Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fs: pass the request_mask to generic_fillattr

2023-08-09T06:56:36+00:00

generic_fillattr just fills in the entire stat struct indiscriminately today, copying data from the inode. There is at least one attribute (STATX_CHANGE_COOKIE) that can have side effects when it is reported, and we're looking at adding more with the addition of multigrain timestamps. Add a request_mask argument to generic_fillattr and have most callers just pass in the value that is passed to getattr. Have other callers (e.g. ksmbd) just pass in STATX_BASIC_STATS. Also move the setting of STATX_CHANGE_COOKIE into generic_fillattr. Acked-by: Joseph Qi Reviewed-by: Xiubo Li Reviewed-by: "Paulo Alcantara (SUSE)" Reviewed-by: Jan Kara Signed-off-by: Jeff Layton Message-Id: <20230807-mgctime-v7-2-d1dec143a704@kernel.org> Signed-off-by: Christian Brauner

Merge tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

2023-02-20T19:53:11+00:00

Pull vfs idmapping updates from Christian Brauner: - Last cycle we introduced the dedicated struct mnt_idmap type for mount idmapping and the required infrastucture in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). As promised in last cycle's pull request message this converts everything to rely on struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevant on the mount level. Especially for non-vfs developers without detailed knowledge in this area this was a potential source for bugs. This finishes the conversion. Instead of passing the plain namespace around this updates all places that currently take a pointer to a mnt_userns with a pointer to struct mnt_idmap. Now that the conversion is done all helpers down to the really low-level helpers only accept a struct mnt_idmap argument instead of two namespace arguments. Conflating mount and other idmappings will now cause the compiler to complain loudly thus eliminating the possibility of any bugs. This makes it impossible for filesystem developers to mix up mount and filesystem idmappings as they are two distinct types and require distinct helpers that cannot be used interchangeably. Everything associated with struct mnt_idmap is moved into a single separate file. With that change no code can poke around in struct mnt_idmap. It can only be interacted with through dedicated helpers. That means all filesystems are and all of the vfs is completely oblivious to the actual implementation of idmappings. We are now also able to extend struct mnt_idmap as we see fit. For example, we can decouple it completely from namespaces for users that don't require or don't want to use them at all. We can also extend the concept of idmappings so we can cover filesystem specific requirements. In combination with the vfs{g,u}id_t work we finished in v6.2 this makes this feature substantially more robust and thus difficult to implement wrong by a given filesystem and also protects the vfs. - Enable idmapped mounts for tmpfs and fulfill a longstanding request. A long-standing request from users had been to make it possible to create idmapped mounts for tmpfs. For example, to share the host's tmpfs mount between multiple sandboxes. This is a prerequisite for some advanced Kubernetes cases. Systemd also has a range of use-cases to increase service isolation. And there are more users of this. However, with all of the other work going on this was way down on the priority list but luckily someone other than ourselves picked this up. As usual the patch is tiny as all the infrastructure work had been done multiple kernel releases ago. In addition to all the tests that we already have I requested that Rodrigo add a dedicated tmpfs testsuite for idmapped mounts to xfstests. It is to be included into xfstests during the v6.3 development cycle. This should add a slew of additional tests. * tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (26 commits) shmem: support idmapped mounts for tmpfs fs: move mnt_idmap fs: port vfs{g,u}id helpers to mnt_idmap fs: port fs{g,u}id helpers to mnt_idmap fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap fs: port i_{g,u}id_{needs_}update() to mnt_idmap quota: port to mnt_idmap fs: port privilege checking helpers to mnt_idmap fs: port inode_owner_or_capable() to mnt_idmap fs: port inode_init_owner() to mnt_idmap fs: port acl to mnt_idmap fs: port xattr to mnt_idmap fs: port ->permission() to pass mnt_idmap fs: port ->fileattr_set() to pass mnt_idmap fs: port ->set_acl() to pass mnt_idmap fs: port ->get_acl() to pass mnt_idmap fs: port ->tmpfile() to pass mnt_idmap fs: port ->rename() to pass mnt_idmap fs: port ->mknod() to pass mnt_idmap fs: port ->mkdir() to pass mnt_idmap ...

fs: port ->permission() to pass mnt_idmap

2023-01-19T08:24:28+00:00

Convert to struct mnt_idmap. Last cycle we merged the necessary infrastructure in 256c8aed2b42 ("fs: introduce dedicated idmap type for mounts"). This is just the conversion to struct mnt_idmap. Currently we still pass around the plain namespace that was attached to a mount. This is in general pretty convenient but it makes it easy to conflate namespaces that are relevant on the filesystem with namespaces that are relevent on the mount level. Especially for non-vfs developers without detailed knowledge in this area this can be a potential source for bugs. Once the conversion to struct mnt_idmap is done all helpers down to the really low-level helpers will take a struct mnt_idmap argument instead of two namespace arguments. This way it becomes impossible to conflate the two eliminating the possibility of any bugs. All of the vfs and all filesystems only operate on struct mnt_idmap. Acked-by: Dave Chinner Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

fs: port ->getattr() to pass mnt_idmap

2023-01-19T08:24:25+00:00

filelock: move file locking definitions to separate header file

2023-01-11T11:52:32+00:00

The file locking definitions have lived in fs.h since the dawn of time, but they are only used by a small subset of the source files that include it. Move the file locking definitions to a new header file, and add the appropriate #include directives to the source files that need them. By doing this we trim down fs.h a bit and limit the amount of rebuilding that has to be done when we make changes to the file locking APIs. Reviewed-by: Xiubo Li Reviewed-by: Christian Brauner (Microsoft) Reviewed-by: Christoph Hellwig Reviewed-by: David Howells Reviewed-by: Russell King (Oracle) Acked-by: Chuck Lever Acked-by: Joseph Qi Acked-by: Steve French Acked-by: Al Viro Acked-by: Darrick J. Wong Signed-off-by: Jeff Layton

proc: report open files as size in stat() for /proc/pid/fd

2022-11-18T21:55:07+00:00

Many monitoring tools include open file count as a metric. Currently the only way to get this number is to enumerate the files in /proc/pid/fd. The problem with the current approach is that it does many things people generally don't care about when they need one number for a metric. In our tests for cadvisor, which reports open file counts per cgroup, we observed that reading the number of open files is slow. Out of 35.23% of CPU time spent in `proc_readfd_common`, we see 29.43% spent in `proc_fill_cache`, which is responsible for filling dentry info. Some of this extra time is spinlock contention, but it's a contention for the lock we don't want to take to begin with. We considered putting the number of open files in /proc/pid/status. Unfortunately, counting the number of fds involves iterating the open_files bitmap, which has a linear complexity in proportion with the number of open files (bitmap slots really, but it's close). We don't want to make /proc/pid/status any slower, so instead we put this info in /proc/pid/fd as a size member of the stat syscall result. Previously the reported number was zero, so there's very little risk of breaking anything, while still providing a somewhat logical way to count the open files with a fallback if it's zero. RFC for this patch included iterating open fds under RCU. Thanks to Frank Hofmann for the suggestion to use the bitmap instead. Previously: ``` $ sudo stat /proc/1/fd | head -n2 File: /proc/1/fd Size: 0 Blocks: 0 IO Block: 1024 directory ``` With this patch: ``` $ sudo stat /proc/1/fd | head -n2 File: /proc/1/fd Size: 65 Blocks: 0 IO Block: 1024 directory ``` Correctness check: ``` $ sudo ls /proc/1/fd | wc -l 65 ``` I added the docs for /proc//fd while I'm at it. [ivan@cloudflare.com: use bitmap_weight() to count the bits] Link: https://lkml.kernel.org/r/20221018045844.37697-1-ivan@cloudflare.com [akpm@linux-foundation.org: include linux/bitmap.h for bitmap_weight()] [ivan@cloudflare.com: return errno from proc_fd_getattr() instead of setting negative size] Link: https://lkml.kernel.org/r/20221024173140.30673-1-ivan@cloudflare.com Link: https://lkml.kernel.org/r/20220922224027.59266-1-ivan@cloudflare.com Signed-off-by: Ivan Babrou Cc: Alexey Dobriyan Cc: Al Viro Cc: Christoph Anton Mitterer Cc: David Hildenbrand Cc: David Laight Cc: Ivan Babrou Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Kalesh Singh Cc: Mike Rapoport Cc: Paul Gortmaker Cc: Theodore Ts'o Signed-off-by: Andrew Morton

procfs: prevent unprivileged processes accessing fdinfo dir

2022-05-10T00:34:28+00:00

The file permissions on the fdinfo dir from were changed from S_IRUSR|S_IXUSR to S_IRUGO|S_IXUGO, and a PTRACE_MODE_READ check was added for opening the fdinfo files [1]. However, the ptrace permission check was not added to the directory, allowing anyone to get the open FD numbers by reading the fdinfo directory. Add the missing ptrace permission check for opening the fdinfo directory. [1] https://lkml.kernel.org/r/20210308170651.919148-1-kaleshsingh@google.com Link: https://lkml.kernel.org/r/20210713162008.1056986-1-kaleshsingh@google.com Fixes: 7bc3fa0172a4 ("procfs: allow reading fdinfo with PTRACE_MODE_READ") Signed-off-by: Kalesh Singh Cc: Kees Cook Cc: Eric W. Biederman Cc: Christian Brauner Cc: Suren Baghdasaryan Cc: Hridya Valsaraju Cc: Jann Horn Signed-off-by: Andrew Morton

procfs/dmabuf: add inode number to /proc/*/fdinfo

2021-07-01T18:06:04+00:00

And 'ino' field to /proc//fdinfo/ and /proc//task//fdinfo/. The inode numbers can be used to uniquely identify DMA buffers in user space and avoids a dependency on /proc//fd/* when accounting per-process DMA buffer sizes. Link: https://lkml.kernel.org/r/20210308170651.919148-2-kaleshsingh@google.com Signed-off-by: Kalesh Singh Acked-by: Randy Dunlap Acked-by: Christian König Cc: Jann Horn Cc: Jeff Vander Stoep Cc: Kees Cook Cc: Suren Baghdasaryan Cc: Minchan Kim Cc: Hridya Valsaraju Cc: Matthew Wilcox Cc: Alexander Viro Cc: Kalesh Singh Cc: Alexey Dobriyan Cc: Jonathan Corbet Cc: Mauro Carvalho Chehab Cc: Michal Hocko Cc: Alexey Gladkov Cc: Szabolcs Nagy Cc: Eric W. Biederman Cc: Christian Brauner Cc: Michel Lespinasse Cc: Bernd Edlinger Cc: Andrei Vagin Cc: Helge Deller Cc: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

procfs: allow reading fdinfo with PTRACE_MODE_READ

2021-07-01T18:06:04+00:00

Android captures per-process system memory state when certain low memory events (e.g a foreground app kill) occur, to identify potential memory hoggers. In order to measure how much memory a process actually consumes, it is necessary to include the DMA buffer sizes for that process in the memory accounting. Since the handle to DMA buffers are raw FDs, it is important to be able to identify which processes have FD references to a DMA buffer. Currently, DMA buffer FDs can be accounted using /proc//fd/* and /proc//fdinfo -- both are only readable by the process owner, as follows: 1. Do a readlink on each FD. 2. If the target path begins with "/dmabuf", then the FD is a dmabuf FD. 3. stat the file to get the dmabuf inode number. 4. Read/ proc//fdinfo/, to get the DMA buffer size. Accessing other processes' fdinfo requires root privileges. This limits the use of the interface to debugging environments and is not suitable for production builds. Granting root privileges even to a system process increases the attack surface and is highly undesirable. Since fdinfo doesn't permit reading process memory and manipulating process state, allow accessing fdinfo under PTRACE_MODE_READ_FSCRED. Link: https://lkml.kernel.org/r/20210308170651.919148-1-kaleshsingh@google.com Signed-off-by: Kalesh Singh Suggested-by: Jann Horn Acked-by: Christian König Cc: Alexander Viro Cc: Alexey Dobriyan Cc: Alexey Gladkov Cc: Andrei Vagin Cc: Bernd Edlinger Cc: Christian Brauner Cc: Eric W. Biederman Cc: Helge Deller Cc: Hridya Valsaraju Cc: James Morris Cc: Jeff Vander Stoep Cc: Jonathan Corbet Cc: Kees Cook Cc: Matthew Wilcox Cc: Mauro Carvalho Chehab Cc: Michal Hocko Cc: Michel Lespinasse Cc: Minchan Kim Cc: Randy Dunlap Cc: Suren Baghdasaryan Cc: Szabolcs Nagy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds