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Message-ID: <20250224-klinke-hochdekoriert-3f6be89005a8@brauner> Date: Mon, 24 Feb 2025 12:32:17 +0100 From: Christian Brauner <brauner@...nel.org> Cc: Amir Goldstein <amir73il@...il.com>, Andrey Albershteyn <aalbersh@...hat.com>, "Darrick J. Wong" <djwong@...nel.org>, 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>, Jan Kara <jack@...e.cz>, Mickaël Salaün <mic@...ikod.net>, Günther Noack <gnoack@...gle.com>, Arnd Bergmann <arnd@...db.de>, 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, Pali Rohár <pali@...nel.org>, Theodore Tso <tytso@....edu> Subject: Re: [PATCH v3] fs: introduce getfsxattrat and setfsxattrat syscalls On Fri, Feb 21, 2025 at 08:15:24PM +0100, Amir Goldstein wrote: > On Fri, Feb 21, 2025 at 7:13 PM Darrick J. Wong <djwong@...nel.org> wrote: > > > > On Tue, Feb 11, 2025 at 06:22:47PM +0100, 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. > > > > > > Also, as vfs_fileattr_set() is now will be called on special files > > > too, let's forbid any other attributes except projid and nextents > > > (symlink can have an extent). > > > > > > 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> > > > --- > > > v1: > > > https://lore.kernel.org/linuxppc-dev/20250109174540.893098-1-aalbersh@kernel.org/ > > > > > > Previous discussion: > > > https://lore.kernel.org/linux-xfs/20240520164624.665269-2-aalbersh@redhat.com/ > > > > > > XFS has project quotas which could be attached to a directory. All > > > new inodes in these directories inherit project ID set on parent > > > directory. > > > > > > The project is created from userspace by opening and calling > > > FS_IOC_FSSETXATTR on each inode. This is not possible for special > > > files such as FIFO, SOCK, BLK etc. Therefore, some inodes are left > > > with empty project ID. Those inodes then are not shown in the quota > > > accounting but still exist in the directory. Moreover, in the case > > > when special files are created in the directory with already > > > existing project quota, these inode inherit extended attributes. > > > This than leaves them with these attributes without the possibility > > > to clear them out. This, in turn, prevents userspace from > > > re-creating quota project on these existing files. > > > --- > > > Changes in v3: > > > - Remove unnecessary "dfd is dir" check as it checked in user_path_at() > > > - Remove unnecessary "same filesystem" check > > > - Use CLASS() instead of directly calling fdget/fdput > > > - Link to v2: https://lore.kernel.org/r/20250122-xattrat-syscall-v2-1-5b360d4fbcb2@kernel.org > > > --- > > > arch/alpha/kernel/syscalls/syscall.tbl | 2 + > > > arch/arm/tools/syscall.tbl | 2 + > > > arch/arm64/tools/syscall_32.tbl | 2 + > > > arch/m68k/kernel/syscalls/syscall.tbl | 2 + > > > arch/microblaze/kernel/syscalls/syscall.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_n32.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_n64.tbl | 2 + > > > arch/mips/kernel/syscalls/syscall_o32.tbl | 2 + > > > arch/parisc/kernel/syscalls/syscall.tbl | 2 + > > > arch/powerpc/kernel/syscalls/syscall.tbl | 2 + > > > arch/s390/kernel/syscalls/syscall.tbl | 2 + > > > arch/sh/kernel/syscalls/syscall.tbl | 2 + > > > arch/sparc/kernel/syscalls/syscall.tbl | 2 + > > > arch/x86/entry/syscalls/syscall_32.tbl | 2 + > > > arch/x86/entry/syscalls/syscall_64.tbl | 2 + > > > arch/xtensa/kernel/syscalls/syscall.tbl | 2 + > > > fs/inode.c | 75 +++++++++++++++++++++++++++++ > > > fs/ioctl.c | 16 +++++- > > > include/linux/fileattr.h | 1 + > > > include/linux/syscalls.h | 4 ++ > > > include/uapi/asm-generic/unistd.h | 8 ++- > > > 21 files changed, 133 insertions(+), 3 deletions(-) > > > > > > > <cut to the syscall definitions> > > > > > diff --git a/fs/inode.c b/fs/inode.c > > > index 6b4c77268fc0ecace4ac78a9ca777fbffc277f4a..b2dddd9db4fabaf67a6cbf541a86978b290411ec 100644 > > > --- a/fs/inode.c > > > +++ b/fs/inode.c > > > @@ -23,6 +23,9 @@ > > > #include <linux/rw_hint.h> > > > #include <linux/seq_file.h> > > > #include <linux/debugfs.h> > > > +#include <linux/syscalls.h> > > > +#include <linux/fileattr.h> > > > +#include <linux/namei.h> > > > #include <trace/events/writeback.h> > > > #define CREATE_TRACE_POINTS > > > #include <trace/events/timestamp.h> > > > @@ -2953,3 +2956,75 @@ umode_t mode_strip_sgid(struct mnt_idmap *idmap, > > > return mode & ~S_ISGID; > > > } > > > EXPORT_SYMBOL(mode_strip_sgid); > > > + > > > +SYSCALL_DEFINE4(getfsxattrat, int, dfd, const char __user *, filename, > > > + struct fsxattr __user *, fsx, unsigned int, at_flags) > > > > Should the kernel require userspace to pass the size of the fsx buffer? > > That way we avoid needing to rev the interface when we decide to grow > > the structure. Please version the struct by size as we do for clone3(), mount_setattr(), listmount()'s struct mnt_id_req, sched_setattr(), all the new xattrat*() system calls and a host of others. So laying out the struct 64bit and passing a size alongside it. This is all handled by copy_struct_from_user() and copy_struct_to_user() so nothing to reinvent. And it's easy to copy from existing system calls.
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