kernel/linux.git/fs/hostfs/hostfs_user.c, branch v6.12.80

um: hostfs: avoid issues on inode number reuse by host

2025-04-10T12:39:25+00:00

[ Upstream commit 0bc754d1e31f40f4a343b692096d9e092ccc0370 ] Some file systems (e.g. ext4) may reuse inode numbers once the inode is not in use anymore. Usually hostfs will keep an FD open for each inode, but this is not always the case. In the case of sockets, this cannot even be done properly. As such, the following sequence of events was possible: * application creates and deletes a socket * hostfs creates/deletes the socket on the host * inode is still in the hostfs cache * hostfs creates a new file * ext4 on the outside reuses the inode number * hostfs finds the socket inode for the newly created file * application receives -ENXIO when opening the file As mentioned, this can only happen if the deleted file is a special file that is never opened on the host (i.e. no .open fop). As such, to prevent issues, it is sufficient to check that the inode has the expected type. That said, also add a check for the inode birth time, just to be on the safe side. Fixes: 74ce793bcbde ("hostfs: Fix ephemeral inodes") Signed-off-by: Benjamin Berg Reviewed-by: Mickaël Salaün Tested-by: Mickaël Salaün Link: https://patch.msgid.link/20250214092822.1241575-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin

hostfs: fix dev_t handling

2024-07-03T10:23:50+00:00

dev_t is a kernel type and may have different definitions in kernel and userspace. On 32-bit x86 this currently makes the stat structure being 4 bytes longer in the user code, causing stack corruption. However, this is (potentially) not the only problem, since dev_t is a different type on user/kernel side, so we don't know that the major/minor encoding isn't also different. Decode/encode it instead to address both problems. Cc: stable@vger.kernel.org Fixes: 74ce793bcbde ("hostfs: Fix ephemeral inodes") Link: https://patch.msgid.link/20240702092440.acc960585dd5.Id0767e12f562a69c6cd3c3262dc3d765db350cf6@changeid Signed-off-by: Johannes Berg

hostfs: Fix ephemeral inodes

2023-06-12T19:26:19+00:00

hostfs creates a new inode for each opened or created file, which created useless inode allocations and forbade identifying a host file with a kernel inode. Fix this uncommon filesystem behavior by tying kernel inodes to host file's inode and device IDs. Even if the host filesystem inodes may be recycled, this cannot happen while a file referencing it is opened, which is the case with hostfs. It should be noted that hostfs inode IDs may not be unique for the same hostfs superblock because multiple host's (backed) superblocks may be used. Delete inodes when dropping them to force backed host's file descriptors closing. This enables to entirely remove ARCH_EPHEMERAL_INODES, and then makes Landlock fully supported by UML. This is very useful for testing changes. These changes also factor out and simplify some helpers thanks to the new hostfs_inode_update() and the hostfs_iget() revamp: read_name(), hostfs_create(), hostfs_lookup(), hostfs_mknod(), and hostfs_fill_sb_common(). A following commit with new Landlock tests check this new hostfs inode consistency. Cc: Anton Ivanov Cc: Johannes Berg Acked-by: Richard Weinberger Link: https://lore.kernel.org/r/20230612191430.339153-2-mic@digikod.net Signed-off-by: Mickaël Salaün

hostfs: rename do_rmdir() to hostfs_do_rmdir()

2018-04-02T18:15:53+00:00

do_rmdir() is used in the VFS layer at fs/namei.c, so use a different name in hostfs. Cc: Jeff Dike Cc: user-mode-linux-devel@lists.sourceforge.net Acked-by: Richard Weinberger Signed-off-by: Dominik Brodowski

um: hostfs: Reduce number of syscalls in readdir

2015-04-13T19:01:07+00:00

Currently hostfs issues every time a seekdir(), in fact it has to do this only upon the first call. Also telldir() can be omitted as we can obtain the directory offset from readdir(). Signed-off-by: Richard Weinberger

hostfs: No need to box and later unbox the file mode

2015-03-26T22:27:53+00:00

There is really no point in having a function with 10 arguments. Reported-by: Daniel Walter Signed-off-by: Richard Weinberger

hostfs: support rename flags

2014-08-07T18:40:09+00:00

Support RENAME_NOREPLACE and RENAME_EXCHANGE flags on hostfs if the underlying filesystem supports it. Since renameat2(2) is not yet in any libc, use syscall(2) to invoke the renameat2 syscall. Signed-off-by: Miklos Szeredi Cc: Richard Weinberger Signed-off-by: Christoph Hellwig Signed-off-by: Al Viro

um: get rid of pointless include "..." where include <...> will do

2012-10-09T20:28:45+00:00

Signed-off-by: Al Viro Signed-off-by: Richard Weinberger

uml/hostfs: Propagate dirent.d_type to filldir()

2012-03-24T23:29:52+00:00

Currently the (optional) d_type member in struct dirent is always DT_UNKNOWN on hostfs, which may confuse buggy software using readdir(). Make sure to propagate its value from the underlying filesystem if it's available there. Signed-off-by: Geert Uytterhoeven Signed-off-by: Richard Weinberger

um: kill useless include of user.h

2011-11-02T13:15:13+00:00

everything in USER_OBJ gets it via -include user.h Signed-off-by: Al Viro Signed-off-by: Richard Weinberger