kernel/linux.git/fs/namei.c, branch v5.15.208

openat2: don't trigger automounts with RESOLVE_NO_XDEV

2025-10-19T14:21:46+00:00

commit 042a60680de43175eb4df0977ff04a4eba9da082 upstream. openat2 had a bug: if we pass RESOLVE_NO_XDEV, then openat2 doesn't traverse through automounts, but may still trigger them. (See the link for full bug report with reproducer.) This commit fixes this bug. Link: https://lore.kernel.org/linux-fsdevel/20250817075252.4137628-1-safinaskar@zohomail.com/ Fixes: fddb5d430ad9fa91b49b1 ("open: introduce openat2(2) syscall") Reviewed-by: Aleksa Sarai Cc: stable@vger.kernel.org Signed-off-by: Askar Safin Link: https://lore.kernel.org/20250825181233.2464822-5-safinaskar@zohomail.com Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fuse: don't truncate cached, mutated symlink

2025-04-10T12:31:51+00:00

[ Upstream commit b4c173dfbb6c78568578ff18f9e8822d7bd0e31b ] Fuse allows the value of a symlink to change and this property is exploited by some filesystems (e.g. CVMFS). It has been observed, that sometimes after changing the symlink contents, the value is truncated to the old size. This is caused by fuse_getattr() racing with fuse_reverse_inval_inode(). fuse_reverse_inval_inode() updates the fuse_inode's attr_version, which results in fuse_change_attributes() exiting before updating the cached attributes This is okay, as the cached attributes remain invalid and the next call to fuse_change_attributes() will likely update the inode with the correct values. The reason this causes problems is that cached symlinks will be returned through page_get_link(), which truncates the symlink to inode->i_size. This is correct for filesystems that don't mutate symlinks, but in this case it causes bad behavior. The solution is to just remove this truncation. This can cause a regression in a filesystem that relies on supplying a symlink larger than the file size, but this is unlikely. If that happens we'd need to make this behavior conditional. Reported-by: Laura Promberger Tested-by: Sam Lewis Signed-off-by: Miklos Szeredi Link: https://lore.kernel.org/r/20250220100258.793363-1-mszeredi@redhat.com Reviewed-by: Bernd Schubert Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

rename(): fix the locking of subdirectories

2024-02-23T07:54:26+00:00

commit 22e111ed6c83dcde3037fc81176012721bc34c0b upstream. We should never lock two subdirectories without having taken ->s_vfs_rename_mutex; inode pointer order or not, the "order" proposed in 28eceeda130f "fs: Lock moved directories" is not transitive, with the usual consequences. The rationale for locking renamed subdirectory in all cases was the possibility of race between rename modifying .. in a subdirectory to reflect the new parent and another thread modifying the same subdirectory. For a lot of filesystems that's not a problem, but for some it can lead to trouble (e.g. the case when short directory contents is kept in the inode, but creating a file in it might push it across the size limit and copy its contents into separate data block(s)). However, we need that only in case when the parent does change - otherwise ->rename() doesn't need to do anything with .. entry in the first place. Some instances are lazy and do a tautological update anyway, but it's really not hard to avoid. Amended locking rules for rename(): find the parent(s) of source and target if source and target have the same parent lock the common parent else lock ->s_vfs_rename_mutex lock both parents, in ancestor-first order; if neither is an ancestor of another, lock the parent of source first. find the source and target. if source and target have the same parent if operation is an overwriting rename of a subdirectory lock the target subdirectory else if source is a subdirectory lock the source if target is a subdirectory lock the target lock non-directories involved, in inode pointer order if both source and target are such. That way we are guaranteed that parents are locked (for obvious reasons), that any renamed non-directory is locked (nfsd relies upon that), that any victim is locked (emptiness check needs that, among other things) and subdirectory that changes parent is locked (needed to protect the update of .. entries). We are also guaranteed that any operation locking more than one directory either takes ->s_vfs_rename_mutex or locks a parent followed by its child. Cc: stable@vger.kernel.org Fixes: 28eceeda130f "fs: Lock moved directories" Reviewed-by: Jan Kara Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

ksmbd: fix racy issue from using ->d_parent and ->d_name

2023-12-23T09:41:55+00:00

[ Upstream commit 74d7970febf7e9005375aeda0df821d2edffc9f7 ] Al pointed out that ksmbd has racy issue from using ->d_parent and ->d_name in ksmbd_vfs_unlink and smb2_vfs_rename(). and use new lock_rename_child() to lock stable parent while underlying rename racy. Introduce vfs_path_parent_lookup helper to avoid out of share access and export vfs functions like the following ones to use vfs_path_parent_lookup(). - rename __lookup_hash() to lookup_one_qstr_excl(). - export lookup_one_qstr_excl(). - export getname_kernel() and putname(). vfs_path_parent_lookup() is used for parent lookup of destination file using absolute pathname given from FILE_RENAME_INFORMATION request. Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

fs: introduce lock_rename_child() helper

2023-12-23T09:41:55+00:00

[ Upstream commit 9bc37e04823b5280dd0f22b6680fc23fe81ca325 ] Pass the dentry of a source file and the dentry of a destination directory to lock parent inodes for rename. As soon as this function returns, ->d_parent of the source file dentry is stable and inodes are properly locked for calling vfs-rename. This helper is needed for ksmbd server. rename request of SMB protocol has to rename an opened file, no matter which directory it's in. Signed-off-by: Al Viro Signed-off-by: Namjae Jeon Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

fs: Fix error checking for d_hash_and_lookup()

2023-09-19T10:22:30+00:00

[ Upstream commit 0d5a4f8f775ff990142cdc810a84eae078589d27 ] The d_hash_and_lookup() function returns error pointers or NULL. Most incorrect error checks were fixed, but the one in int path_pts() was forgotten. Fixes: eedf265aa003 ("devpts: Make each mount of devpts an independent filesystem.") Signed-off-by: Wang Ming Message-Id: <20230713120555.7025-1-machel@vivo.com> Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin

fs: no need to check source

2023-07-23T11:47:36+00:00

commit 66d8fc0539b0d49941f313c9509a8384e4245ac1 upstream. The @source inode must be valid. It is even checked via IS_SWAPFILE() above making it pretty clear. So no need to check it when we unlock. What doesn't need to exist is the @target inode. The lock_two_inodes() helper currently swaps the @inode1 and @inode2 arguments if @inode1 is NULL to have consistent lock class usage. However, we know that at least for vfs_rename() that @inode1 is @source and thus is never NULL as per above. We also know that @source is a different inode than @target as that is checked right at the beginning of vfs_rename(). So we know that @source is valid and locked and that @target is locked. So drop the check whether @source is non-NULL. Fixes: 28eceeda130f ("fs: Lock moved directories") Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202307030026.9sE2pk2x-lkp@intel.com Message-Id: <20230703-vfs-rename-source-v1-1-37eebb29b65b@kernel.org> [brauner: use commit message from patch I sent concurrently] Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fs: Lock moved directories

2023-07-23T11:47:34+00:00

commit 28eceeda130f5058074dd007d9c59d2e8bc5af2e upstream. When a directory is moved to a different directory, some filesystems (udf, ext4, ocfs2, f2fs, and likely gfs2, reiserfs, and others) need to update their pointer to the parent and this must not race with other operations on the directory. Lock the directories when they are moved. Although not all filesystems need this locking, we perform it in vfs_rename() because getting the lock ordering right is really difficult and we don't want to expose these locking details to filesystems. CC: stable@vger.kernel.org Signed-off-by: Jan Kara Message-Id: <20230601105830.13168-5-jack@suse.cz> Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fs: Establish locking order for unrelated directories

2023-07-23T11:47:33+00:00

commit f23ce757185319886ca80c4864ce5f81ac6cc9e9 upstream. Currently the locking order of inode locks for directories that are not in ancestor relationship is not defined because all operations that needed to lock two directories like this were serialized by sb->s_vfs_rename_mutex. However some filesystems need to lock two subdirectories for RENAME_EXCHANGE operations and for this we need the locking order established even for two tree-unrelated directories. Provide a helper function lock_two_inodes() that establishes lock ordering for any two inodes and use it in lock_two_directories(). CC: stable@vger.kernel.org Signed-off-by: Jan Kara Message-Id: <20230601105830.13168-4-jack@suse.cz> Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

fs: move S_ISGID stripping into the vfs_*() helpers

2023-03-17T07:49:00+00:00

commit 1639a49ccdce58ea248841ed9b23babcce6dbb0b upsream. Move setgid handling out of individual filesystems and into the VFS itself to stop the proliferation of setgid inheritance bugs. Creating files that have both the S_IXGRP and S_ISGID bit raised in directories that themselves have the S_ISGID bit set requires additional privileges to avoid security issues. When a filesystem creates a new inode it needs to take care that the caller is either in the group of the newly created inode or they have CAP_FSETID in their current user namespace and are privileged over the parent directory of the new inode. If any of these two conditions is true then the S_ISGID bit can be raised for an S_IXGRP file and if not it needs to be stripped. However, there are several key issues with the current implementation: * S_ISGID stripping logic is entangled with umask stripping. If a filesystem doesn't support or enable POSIX ACLs then umask stripping is done directly in the vfs before calling into the filesystem. If the filesystem does support POSIX ACLs then unmask stripping may be done in the filesystem itself when calling posix_acl_create(). Since umask stripping has an effect on S_ISGID inheritance, e.g., by stripping the S_IXGRP bit from the file to be created and all relevant filesystems have to call posix_acl_create() before inode_init_owner() where we currently take care of S_ISGID handling S_ISGID handling is order dependent. IOW, whether or not you get a setgid bit depends on POSIX ACLs and umask and in what order they are called. Note that technically filesystems are free to impose their own ordering between posix_acl_create() and inode_init_owner() meaning that there's additional ordering issues that influence S_SIGID inheritance. * Filesystems that don't rely on inode_init_owner() don't get S_ISGID stripping logic. While that may be intentional (e.g. network filesystems might just defer setgid stripping to a server) it is often just a security issue. This is not just ugly it's unsustainably messy especially since we do still have bugs in this area years after the initial round of setgid bugfixes. So the current state is quite messy and while we won't be able to make it completely clean as posix_acl_create() is still a filesystem specific call we can improve the S_SIGD stripping situation quite a bit by hoisting it out of inode_init_owner() and into the vfs creation operations. This means we alleviate the burden for filesystems to handle S_ISGID stripping correctly and can standardize the ordering between S_ISGID and umask stripping in the vfs. We add a new helper vfs_prepare_mode() so S_ISGID handling is now done in the VFS before umask handling. This has S_ISGID handling is unaffected unaffected by whether umask stripping is done by the VFS itself (if no POSIX ACLs are supported or enabled) or in the filesystem in posix_acl_create() (if POSIX ACLs are supported). The vfs_prepare_mode() helper is called directly in vfs_*() helpers that create new filesystem objects. We need to move them into there to make sure that filesystems like overlayfs hat have callchains like: sys_mknod() -> do_mknodat(mode) -> .mknod = ovl_mknod(mode) -> ovl_create(mode) -> vfs_mknod(mode) get S_ISGID stripping done when calling into lower filesystems via vfs_*() creation helpers. Moving vfs_prepare_mode() into e.g. vfs_mknod() takes care of that. This is in any case semantically cleaner because S_ISGID stripping is VFS security requirement. Security hooks so far have seen the mode with the umask applied but without S_ISGID handling done. The relevant hooks are called outside of vfs_*() creation helpers so by calling vfs_prepare_mode() from vfs_*() helpers the security hooks would now see the mode without umask stripping applied. For now we fix this by passing the mode with umask settings applied to not risk any regressions for LSM hooks. IOW, nothing changes for LSM hooks. It is worth pointing out that security hooks never saw the mode that is seen by the filesystem when actually creating the file. They have always been completely misplaced for that to work. The following filesystems use inode_init_owner() and thus relied on S_ISGID stripping: spufs, 9p, bfs, btrfs, ext2, ext4, f2fs, hfsplus, hugetlbfs, jfs, minix, nilfs2, ntfs3, ocfs2, omfs, overlayfs, ramfs, reiserfs, sysv, ubifs, udf, ufs, xfs, zonefs, bpf, tmpfs. All of the above filesystems end up calling inode_init_owner() when new filesystem objects are created through the ->mkdir(), ->mknod(), ->create(), ->tmpfile(), ->rename() inode operations. Since directories always inherit the S_ISGID bit with the exception of xfs when irix_sgid_inherit mode is turned on S_ISGID stripping doesn't apply. The ->symlink() and ->link() inode operations trivially inherit the mode from the target and the ->rename() inode operation inherits the mode from the source inode. All other creation inode operations will get S_ISGID handling via vfs_prepare_mode() when called from their relevant vfs_*() helpers. In addition to this there are filesystems which allow the creation of filesystem objects through ioctl()s or - in the case of spufs - circumventing the vfs in other ways. If filesystem objects are created through ioctl()s the vfs doesn't know about it and can't apply regular permission checking including S_ISGID logic. Therfore, a filesystem relying on S_ISGID stripping in inode_init_owner() in their ioctl() callpath will be affected by moving this logic into the vfs. We audited those filesystems: * btrfs allows the creation of filesystem objects through various ioctls(). Snapshot creation literally takes a snapshot and so the mode is fully preserved and S_ISGID stripping doesn't apply. Creating a new subvolum relies on inode_init_owner() in btrfs_new_subvol_inode() but only creates directories and doesn't raise S_ISGID. * ocfs2 has a peculiar implementation of reflinks. In contrast to e.g. xfs and btrfs FICLONE/FICLONERANGE ioctl() that is only concerned with the actual extents ocfs2 uses a separate ioctl() that also creates the target file. Iow, ocfs2 circumvents the vfs entirely here and did indeed rely on inode_init_owner() to strip the S_ISGID bit. This is the only place where a filesystem needs to call mode_strip_sgid() directly but this is self-inflicted pain. * spufs doesn't go through the vfs at all and doesn't use ioctl()s either. Instead it has a dedicated system call spufs_create() which allows the creation of filesystem objects. But spufs only creates directories and doesn't allo S_SIGID bits, i.e. it specifically only allows 0777 bits. * bpf uses vfs_mkobj() but also doesn't allow S_ISGID bits to be created. The patch will have an effect on ext2 when the EXT2_MOUNT_GRPID mount option is used, on ext4 when the EXT4_MOUNT_GRPID mount option is used, and on xfs when the XFS_FEAT_GRPID mount option is used. When any of these filesystems are mounted with their respective GRPID option then newly created files inherit the parent directories group unconditionally. In these cases non of the filesystems call inode_init_owner() and thus did never strip the S_ISGID bit for newly created files. Moving this logic into the VFS means that they now get the S_ISGID bit stripped. This is a user visible change. If this leads to regressions we will either need to figure out a better way or we need to revert. However, given the various setgid bugs that we found just in the last two years this is a regression risk we should take. Associated with this change is a new set of fstests to enforce the semantics for all new filesystems. Link: https://lore.kernel.org/ceph-devel/20220427092201.wvsdjbnc7b4dttaw@wittgenstein [1] Link: e014f37db1a2 ("xfs: use setattr_copy to set vfs inode attributes") [2] Link: 01ea173e103e ("xfs: fix up non-directory creation in SGID directories") [3] Link: fd84bfdddd16 ("ceph: fix up non-directory creation in SGID directories") [4] Link: https://lore.kernel.org/r/1657779088-2242-3-git-send-email-xuyang2018.jy@fujitsu.com Suggested-by: Dave Chinner Suggested-by: Christian Brauner (Microsoft) Reviewed-by: Darrick J. Wong Reviewed-and-Tested-by: Jeff Layton Signed-off-by: Yang Xu [: rewrote commit message] Signed-off-by: Christian Brauner (Microsoft) Signed-off-by: Amir Goldstein Tested-by: Leah Rumancik Acked-by: Darrick J. Wong Signed-off-by: Sasha Levin