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Message-ID: <qyiozv4dtkqlp5wuyhocpptngs5wpuhyouhfqf7vaagkbobsv7@ez3cvpjdyj6q>
Date: Thu, 27 Mar 2025 13:31:50 +0100
From: Jan Kara <jack@...e.cz>
To: Andrey Albershteyn <aalbersh@...hat.com>
Cc: Richard Henderson <richard.henderson@...aro.org>,
Matt Turner <mattst88@...il.com>, Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>, Michal Simek <monstr@...str.eu>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>, "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
Helge Deller <deller@....de>, Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>, Naveen N Rao <naveen@...nel.org>,
Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>, Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Rich Felker <dalias@...c.org>, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
"David S. Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>,
Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Chris Zankel <chris@...kel.net>, Max Filippov <jcmvbkbc@...il.com>,
Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
Mickaël Salaün <mic@...ikod.net>, Günther Noack <gnoack@...gle.com>,
Arnd Bergmann <arnd@...db.de>, Pali Rohár <pali@...nel.org>,
Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>, linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
linux-sh@...r.kernel.org, sparclinux@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
linux-xfs@...r.kernel.org
Subject: Re: [PATCH v4 3/3] fs: introduce getfsxattrat and setfsxattrat
syscalls
On Fri 21-03-25 20:48:42, Andrey Albershteyn wrote:
> From: Andrey Albershteyn <aalbersh@...hat.com>
>
> Introduce getfsxattrat and setfsxattrat syscalls to manipulate inode
> extended attributes/flags. The syscalls take parent directory fd and
> path to the child together with struct fsxattr.
>
> This is an alternative to FS_IOC_FSSETXATTR ioctl with a difference
> that file don't need to be open as we can reference it with a path
> instead of fd. By having this we can manipulated inode extended
> attributes not only on regular files but also on special ones. This
> is not possible with FS_IOC_FSSETXATTR ioctl as with special files
> we can not call ioctl() directly on the filesystem inode using fd.
>
> This patch adds two new syscalls which allows userspace to get/set
> extended inode attributes on special files by using parent directory
> and a path - *at() like syscall.
>
> CC: linux-api@...r.kernel.org
> CC: linux-fsdevel@...r.kernel.org
> CC: linux-xfs@...r.kernel.org
> Signed-off-by: Andrey Albershteyn <aalbersh@...hat.com>
> Acked-by: Arnd Bergmann <arnd@...db.de>
Looks good. Just two nits below:
> +SYSCALL_DEFINE5(getfsxattrat, int, dfd, const char __user *, filename,
> + struct fsxattr __user *, ufsx, size_t, usize,
> + unsigned int, at_flags)
> +{
> + struct fileattr fa = {};
> + struct path filepath;
> + int error;
> + unsigned int lookup_flags = 0;
> + struct filename *name;
> + struct fsxattr fsx = {};
> +
> + BUILD_BUG_ON(sizeof(struct fsxattr) < FSXATTR_SIZE_VER0);
> + BUILD_BUG_ON(sizeof(struct fsxattr) != FSXATTR_SIZE_LATEST);
> +
> + if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
> + return -EINVAL;
> +
> + if (!(at_flags & AT_SYMLINK_NOFOLLOW))
> + lookup_flags |= LOOKUP_FOLLOW;
> +
> + if (at_flags & AT_EMPTY_PATH)
> + lookup_flags |= LOOKUP_EMPTY;
Strictly speaking setting LOOKUP_EMPTY does not have any effect because
empty names are already handled by getname_maybe_null(). But it does not
hurt either so I don't really care...
> +
> + if (usize > PAGE_SIZE)
> + return -E2BIG;
> +
> + if (usize < FSXATTR_SIZE_VER0)
> + return -EINVAL;
> +
> + name = getname_maybe_null(filename, at_flags);
> + if (!name) {
> + CLASS(fd, f)(dfd);
> +
> + if (fd_empty(f))
> + return -EBADF;
> + error = vfs_fileattr_get(file_dentry(fd_file(f)), &fa);
> + } else {
> + error = filename_lookup(dfd, name, lookup_flags, &filepath,
> + NULL);
> + if (error)
> + goto out;
> + error = vfs_fileattr_get(filepath.dentry, &fa);
> + path_put(&filepath);
> + }
> + if (error == -ENOIOCTLCMD)
> + error = -EOPNOTSUPP;
> + if (!error) {
> + fileattr_to_fsxattr(&fa, &fsx);
> + error = copy_struct_to_user(ufsx, usize, &fsx,
> + sizeof(struct fsxattr), NULL);
> + }
> +out:
> + putname(name);
> + return error;
> +}
> +
> +SYSCALL_DEFINE5(setfsxattrat, int, dfd, const char __user *, filename,
> + struct fsxattr __user *, ufsx, size_t, usize,
> + unsigned int, at_flags)
> +{
> + struct fileattr fa;
> + struct path filepath;
> + int error;
> + unsigned int lookup_flags = 0;
> + struct filename *name;
> + struct mnt_idmap *idmap;
> + struct dentry *dentry;
> + struct vfsmount *mnt;
> + struct fsxattr fsx = {};
> +
> + BUILD_BUG_ON(sizeof(struct fsxattr) < FSXATTR_SIZE_VER0);
> + BUILD_BUG_ON(sizeof(struct fsxattr) != FSXATTR_SIZE_LATEST);
> +
> + if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
> + return -EINVAL;
> +
> + if (!(at_flags & AT_SYMLINK_NOFOLLOW))
> + lookup_flags |= LOOKUP_FOLLOW;
> +
> + if (at_flags & AT_EMPTY_PATH)
> + lookup_flags |= LOOKUP_EMPTY;
Same comment regarding LOOKUP_EMPTY here.
> +
> + if (usize > PAGE_SIZE)
> + return -E2BIG;
> +
> + if (usize < FSXATTR_SIZE_VER0)
> + return -EINVAL;
> +
> + error = copy_struct_from_user(&fsx, sizeof(struct fsxattr), ufsx, usize);
> + if (error)
> + return error;
> +
> + fsxattr_to_fileattr(&fsx, &fa);
> +
> + name = getname_maybe_null(filename, at_flags);
> + if (!name) {
> + CLASS(fd, f)(dfd);
> +
> + if (fd_empty(f))
> + return -EBADF;
> +
> + idmap = file_mnt_idmap(fd_file(f));
> + dentry = file_dentry(fd_file(f));
> + mnt = fd_file(f)->f_path.mnt;
> + } else {
> + error = filename_lookup(dfd, name, lookup_flags, &filepath,
> + NULL);
> + if (error)
> + return error;
> +
> + idmap = mnt_idmap(filepath.mnt);
> + dentry = filepath.dentry;
> + mnt = filepath.mnt;
> + }
> +
> + error = mnt_want_write(mnt);
> + if (!error) {
> + error = vfs_fileattr_set(idmap, dentry, &fa);
> + if (error == -ENOIOCTLCMD)
> + error = -EOPNOTSUPP;
> + mnt_drop_write(mnt);
> + }
> +
> + path_put(&filepath);
filepath will not be initialized here in case of name == NULL.
> + return error;
> +}
With this fixed feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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