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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfsLinus Torvalds authored
Pull procfs updates from Christian Brauner: "This contains the following changes for procfs: - Add config options and parameters to block forcing memory writes. This adds a Kconfig option and boot param to allow removing the FOLL_FORCE flag from /proc/<pid>/mem write calls as this can be used in various attacks. The traditional forcing behavior is kept as default because it can break GDB and some other use cases. This is the simpler version that you had requested. - Restrict overmounting of ephemeral entities. It is currently possible to mount on top of various ephemeral entities in procfs. This specifically includes magic links. To recap, magic links are links of the form /proc/<pid>/fd/<nr>. They serve as references to a target file and during path lookup they cause a jump to the target path. Such magic links disappear if the corresponding file descriptor is closed. Currently it is possible to overmount such magic links. This is mostly interesting for an attacker that wants to somehow trick a process into e.g., reopening something that it didn't intend to reopen or to hide a malicious file descriptor. But also it risks leaking mounts for long-running processes. When overmounting a magic link like above, the mount will not be detached when the file descriptor is closed. Only the target mountpoint will disappear. Which has the consequence of making it impossible to unmount that mount afterwards. So the mount will stick around until the process exits and the /proc/<pid>/ directory is cleaned up during proc_flush_pid() when the dentries are pruned and invalidated. That in turn means it's possible for a program to accidentally leak mounts and it's also possible to make a task leak mounts without it's knowledge if the attacker just keeps overmounting things under /proc/<pid>/fd/<nr>. Disallow overmounting of such ephemeral entities. - Cleanup the readdir method naming in some procfs file operations. - Replace kmalloc() and strcpy() with a simple kmemdup() call" * tag 'vfs-6.12.procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: proc: fold kmalloc() + strcpy() into kmemdup() proc: block mounting on top of /proc/<pid>/fdinfo/* proc: block mounting on top of /proc/<pid>/fd/* proc: block mounting on top of /proc/<pid>/map_files/* proc: add proc_splice_unmountable() proc: proc_readfdinfo() -> proc_fdinfo_iterate() proc: proc_readfd() -> proc_fd_iterate() proc: add config & param to block forcing mem writes
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