user/sven/linux.git/include/linux/namei.h, branch v6.1.112

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

2024-01-05T14:18:29Z

[ 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: Sasha Levin

fs: introduce lock_rename_child() helper

2024-01-05T14:18:29Z

[ 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: Sasha Levin

nd_jump_link(): constify path

2022-09-01T21:39:49Z

Reviewed-by: Christian Brauner (Microsoft) Signed-off-by: Al Viro

fs: add two trivial lookup helpers

2022-04-28T14:31:10Z

Similar to the addition of lookup_one() add a version of lookup_one_unlocked() and lookup_one_positive_unlocked() that take idmapped mounts into account. This is required to port overlay to support idmapped base layers. Cc: Tested-by: Giuseppe Scrivano Reviewed-by: Amir Goldstein Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft) Signed-off-by: Miklos Szeredi

namei: add mapping aware lookup helper

2021-08-23T11:19:12Z

Various filesystems rely on the lookup_one_len() helper to lookup a single path component relative to a well-known starting point. Allow such filesystems to support idmapped mounts by adding a version of this helper to take the idmap into account when calling inode_permission(). This change is a required to let btrfs (and other filesystems) support idmapped mounts. Cc: Christoph Hellwig Cc: Al Viro Cc: Matthew Wilcox (Oracle) Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Josef Bacik Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner Signed-off-by: David Sterba

take LOOKUP_{ROOT,ROOT_GRABBED,JUMPED} out of LOOKUP_... space

2021-04-07T17:57:13Z

Separate field in nameidata (nd->state) holding the flags that should be internal-only - that way we both get some spare bits in LOOKUP_... and get simpler rules for nd->root lifetime rules, since we can set the replacement of LOOKUP_ROOT (ND_ROOT_PRESET) at the same time we set nd->root. Signed-off-by: Al Viro

fs: add support for LOOKUP_CACHED

2021-01-04T16:42:21Z

io_uring always punts opens to async context, since there's no control over whether the lookup blocks or not. Add LOOKUP_CACHED to support just doing the fast RCU based lookups, which we know will not block. If we can do a cached path resolution of the filename, then we don't have to always punt lookups for a worker. During path resolution, we always do LOOKUP_RCU first. If that fails and we terminate LOOKUP_RCU, then fail a LOOKUP_CACHED attempt as well. Cc: Al Viro Signed-off-by: Jens Axboe Signed-off-by: Al Viro

sanitize handling of nd->last_type, kill LAST_BIND

2020-03-14T01:08:19Z

->last_type values are set in 3 places: path_init() (sets to LAST_ROOT), link_path_walk (LAST_NORM/DOT/DOTDOT) and pick_link (LAST_BIND). The are checked in walk_component(), lookup_last() and do_last(). They also get copied to the caller by filename_parentat(). In the last 3 cases the value is what we had at the return from link_path_walk(). In case of walk_component() it's either directly downstream from assignment in link_path_walk() or, when called by lookup_last(), the value we have at the return from link_path_walk(). The value at the entry into link_path_walk() can survive to return only if the pathname contains nothing but slashes. Note that pick_link() never returns such - pure jumps are handled directly. So for the calls of link_path_walk() for trailing symlinks it does not matter what value had been there at the entry; the value at the return won't depend upon it. There are 3 call chains that might have pick_link() storing LAST_BIND: 1) pick_link() from step_into() from walk_component() from link_path_walk(). In that case we will either be parsing the next component immediately after return into link_path_walk(), which will overwrite the ->last_type before anyone has a chance to look at it, or we'll fail, in which case nobody will be looking at ->last_type at all. 2) pick_link() from step_into() from walk_component() from lookup_last(). The value is never looked at due to the above; it won't affect the value seen at return from any link_path_walk(). 3) pick_link() from step_into() from do_last(). Ditto. In other words, assignemnt in pick_link() is pointless, and so is LAST_BIND itself; nothing ever looks at that value. Kill it off. And make link_path_walk() _always_ assign ->last_type - in the only case when the value at the entry might survive to the return that value is always LAST_ROOT, inherited from path_init(). Move that assignment from path_init() into the beginning of link_path_walk(), to consolidate the things. Historical note: LAST_BIND used to be used for the kludge with trailing pure jump symlinks (extra iteration through the top-level loop). No point keeping it anymore... Signed-off-by: Al Viro

LOOKUP_MOUNTPOINT: fold path_mountpointat() into path_lookupat()

2020-03-14T01:08:17Z

New LOOKUP flag, telling path_lookupat() to act as path_mountpointat(). IOW, traverse mounts at the final point and skip revalidation of the location where it ends up. Signed-off-by: Al Viro

Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2020-01-29T19:20:24Z

Pull openat2 support from Al Viro: "This is the openat2() series from Aleksa Sarai. I'm afraid that the rest of namei stuff will have to wait - it got zero review the last time I'd posted #work.namei, and there had been a leak in the posted series I'd caught only last weekend. I was going to repost it on Monday, but the window opened and the odds of getting any review during that... Oh, well. Anyway, openat2 part should be ready; that _did_ get sane amount of review and public testing, so here it comes" From Aleksa's description of the series: "For a very long time, extending openat(2) with new features has been incredibly frustrating. This stems from the fact that openat(2) is possibly the most famous counter-example to the mantra "don't silently accept garbage from userspace" -- it doesn't check whether unknown flags are present[1]. This means that (generally) the addition of new flags to openat(2) has been fraught with backwards-compatibility issues (O_TMPFILE has to be defined as __O_TMPFILE|O_DIRECTORY|[O_RDWR or O_WRONLY] to ensure old kernels gave errors, since it's insecure to silently ignore the flag[2]). All new security-related flags therefore have a tough road to being added to openat(2). Furthermore, the need for some sort of control over VFS's path resolution (to avoid malicious paths resulting in inadvertent breakouts) has been a very long-standing desire of many userspace applications. This patchset is a revival of Al Viro's old AT_NO_JUMPS[3] patchset (which was a variant of David Drysdale's O_BENEATH patchset[4] which was a spin-off of the Capsicum project[5]) with a few additions and changes made based on the previous discussion within [6] as well as others I felt were useful. In line with the conclusions of the original discussion of AT_NO_JUMPS, the flag has been split up into separate flags. However, instead of being an openat(2) flag it is provided through a new syscall openat2(2) which provides several other improvements to the openat(2) interface (see the patch description for more details). The following new LOOKUP_* flags are added: LOOKUP_NO_XDEV: Blocks all mountpoint crossings (upwards, downwards, or through absolute links). Absolute pathnames alone in openat(2) do not trigger this. Magic-link traversal which implies a vfsmount jump is also blocked (though magic-link jumps on the same vfsmount are permitted). LOOKUP_NO_MAGICLINKS: Blocks resolution through /proc/$pid/fd-style links. This is done by blocking the usage of nd_jump_link() during resolution in a filesystem. The term "magic-links" is used to match with the only reference to these links in Documentation/, but I'm happy to change the name. It should be noted that this is different to the scope of ~LOOKUP_FOLLOW in that it applies to all path components. However, you can do openat2(NO_FOLLOW|NO_MAGICLINKS) on a magic-link and it will *not* fail (assuming that no parent component was a magic-link), and you will have an fd for the magic-link. In order to correctly detect magic-links, the introduction of a new LOOKUP_MAGICLINK_JUMPED state flag was required. LOOKUP_BENEATH: Disallows escapes to outside the starting dirfd's tree, using techniques such as ".." or absolute links. Absolute paths in openat(2) are also disallowed. Conceptually this flag is to ensure you "stay below" a certain point in the filesystem tree -- but this requires some additional to protect against various races that would allow escape using "..". Currently LOOKUP_BENEATH implies LOOKUP_NO_MAGICLINKS, because it can trivially beam you around the filesystem (breaking the protection). In future, there might be similar safety checks done as in LOOKUP_IN_ROOT, but that requires more discussion. In addition, two new flags are added that expand on the above ideas: LOOKUP_NO_SYMLINKS: Does what it says on the tin. No symlink resolution is allowed at all, including magic-links. Just as with LOOKUP_NO_MAGICLINKS this can still be used with NOFOLLOW to open an fd for the symlink as long as no parent path had a symlink component. LOOKUP_IN_ROOT: This is an extension of LOOKUP_BENEATH that, rather than blocking attempts to move past the root, forces all such movements to be scoped to the starting point. This provides chroot(2)-like protection but without the cost of a chroot(2) for each filesystem operation, as well as being safe against race attacks that chroot(2) is not. If a race is detected (as with LOOKUP_BENEATH) then an error is generated, and similar to LOOKUP_BENEATH it is not permitted to cross magic-links with LOOKUP_IN_ROOT. The primary need for this is from container runtimes, which currently need to do symlink scoping in userspace[7] when opening paths in a potentially malicious container. There is a long list of CVEs that could have bene mitigated by having RESOLVE_THIS_ROOT (such as CVE-2017-1002101, CVE-2017-1002102, CVE-2018-15664, and CVE-2019-5736, just to name a few). In order to make all of the above more usable, I'm working on libpathrs[8] which is a C-friendly library for safe path resolution. It features a userspace-emulated backend if the kernel doesn't support openat2(2). Hopefully we can get userspace to switch to using it, and thus get openat2(2) support for free once it's ready. Future work would include implementing things like RESOLVE_NO_AUTOMOUNT and possibly a RESOLVE_NO_REMOTE (to allow programs to be sure they don't hit DoSes though stale NFS handles)" * 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: Documentation: path-lookup: include new LOOKUP flags selftests: add openat2(2) selftests open: introduce openat2(2) syscall namei: LOOKUP_{IN_ROOT,BENEATH}: permit limited ".." resolution namei: LOOKUP_IN_ROOT: chroot-like scoped resolution namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution namei: LOOKUP_NO_XDEV: block mountpoint crossing namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution namei: LOOKUP_NO_SYMLINKS: block symlink resolution namei: allow set_root() to produce errors namei: allow nd_jump_link() to produce errors nsfs: clean-up ns_get_path() signature to return int namei: only return -ECHILD from follow_dotdot_rcu()