On Tue, May 21, 2024 at 04:06:15PM +0200, Christian Brauner wrote:
> On Mon, May 20, 2024 at 10:51:59AM -0700, Darrick J. Wong wrote:
> > On Mon, May 20, 2024 at 06:46:21PM +0200, Andrey Albershteyn wrote:
> > > 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. as opening them returns a special
> > > inode from VFS. 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.
> > >
> > > This patch adds two new ioctls which allows userspace, such as
> > > xfs_quota, to set project ID on special files by using parent
> > > directory to open FS inode. This will let xfs_quota set ID on all
> > > inodes and also reset it when project is removed. Also, as
> > > vfs_fileattr_set() is now will called on special files too, let's
> > > forbid any other attributes except projid and nextents (symlink can
> > > have one).
> > >
> > > Signed-off-by: Andrey Albershteyn <aalbersh@xxxxxxxxxx>
> > > ---
> > > fs/ioctl.c | 93 +++++++++++++++++++++++++++++++++++++++++
> > > include/uapi/linux/fs.h | 11 +++++
> > > 2 files changed, 104 insertions(+)
> > >
> > > diff --git a/fs/ioctl.c b/fs/ioctl.c
> > > index 1d5abfdf0f22..3e3aacb6ea6e 100644
> > > --- a/fs/ioctl.c
> > > +++ b/fs/ioctl.c
> > > @@ -22,6 +22,7 @@
> > > #include <linux/mount.h>
> > > #include <linux/fscrypt.h>
> > > #include <linux/fileattr.h>
> > > +#include <linux/namei.h>
> > >
> > > #include "internal.h"
> > >
> > > @@ -647,6 +648,19 @@ static int fileattr_set_prepare(struct inode *inode,
> > > if (fa->fsx_cowextsize == 0)
> > > fa->fsx_xflags &= ~FS_XFLAG_COWEXTSIZE;
> > >
> > > + /*
> > > + * The only use case for special files is to set project ID, forbid any
> > > + * other attributes
> > > + */
> > > + if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) {
> > > + if (fa->fsx_xflags & ~FS_XFLAG_PROJINHERIT)
> >
> > When would PROJINHERIT be set on a non-reg/non-dir file?
> >
> > > + return -EINVAL;
> > > + if (!S_ISLNK(inode->i_mode) && fa->fsx_nextents)
> >
> > FS_IOC_FSSETXATTR doesn't enforce anything for fsx_nextents for any
> > other type of file, does it?
> >
> > > + return -EINVAL;
> > > + if (fa->fsx_extsize || fa->fsx_cowextsize)
> > > + return -EINVAL;
> > > + }
> > > +
> > > return 0;
> > > }
> > >
> > > @@ -763,6 +777,79 @@ static int ioctl_fssetxattr(struct file *file, void __user *argp)
> > > return err;
> > > }
> > >
> > > +static int ioctl_fsgetxattrat(struct file *file, void __user *argp)
> > > +{
> > > + struct path filepath;
> > > + struct fsxattrat fsxat;
> > > + struct fileattr fa;
> > > + int error;
> > > +
> > > + if (!S_ISDIR(file_inode(file)->i_mode))
> > > + return -EBADF;
> > > +
> > > + if (copy_from_user(&fsxat, argp, sizeof(struct fsxattrat)))
> > > + return -EFAULT;
> > > +
> > > + error = user_path_at(fsxat.dfd, fsxat.path, 0, &filepath);
> > > + if (error)
> > > + return error;
> > > +
> > > + error = vfs_fileattr_get(filepath.dentry, &fa);
> > > + if (error) {
> > > + path_put(&filepath);
> > > + return error;
> > > + }
> > > +
> > > + fsxat.fsx.fsx_xflags = fa.fsx_xflags;
> > > + fsxat.fsx.fsx_extsize = fa.fsx_extsize;
> > > + fsxat.fsx.fsx_nextents = fa.fsx_nextents;
> > > + fsxat.fsx.fsx_projid = fa.fsx_projid;
> > > + fsxat.fsx.fsx_cowextsize = fa.fsx_cowextsize;
> > > +
> > > + if (copy_to_user(argp, &fsxat, sizeof(struct fsxattrat)))
> > > + error = -EFAULT;
> > > +
> > > + path_put(&filepath);
> > > + return error;
> > > +}
> > > +
> > > +static int ioctl_fssetxattrat(struct file *file, void __user *argp)
> > > +{
> > > + struct mnt_idmap *idmap = file_mnt_idmap(file);
> > > + struct fsxattrat fsxat;
> > > + struct path filepath;
> > > + struct fileattr fa;
> > > + int error;
> > > +
> > > + if (!S_ISDIR(file_inode(file)->i_mode))
> > > + return -EBADF;
> > > +
> > > + if (copy_from_user(&fsxat, argp, sizeof(struct fsxattrat)))
> > > + return -EFAULT;
> > > +
> > > + error = user_path_at(fsxat.dfd, fsxat.path, 0, &filepath);
> > > + if (error)
> > > + return error;
> > > +
> > > + error = mnt_want_write(filepath.mnt);
> > > + if (error) {
> > > + path_put(&filepath);
> > > + return error;
> >
> > This could be a goto to the path_put below.
>
> (Unrelated to content but we should probably grow cleanup guards for
> path_get()/path_put() and mnt_want_write()/mnt_drop_write() then stuff
> like this becomes a no-brainer.)
>
> >
> > > + }
> > > +
> > > + fileattr_fill_xflags(&fa, fsxat.fsx.fsx_xflags);
> > > + fa.fsx_extsize = fsxat.fsx.fsx_extsize;
> > > + fa.fsx_nextents = fsxat.fsx.fsx_nextents;
> > > + fa.fsx_projid = fsxat.fsx.fsx_projid;
> > > + fa.fsx_cowextsize = fsxat.fsx.fsx_cowextsize;
> > > + fa.fsx_valid = true;
> > > +
> > > + error = vfs_fileattr_set(idmap, filepath.dentry, &fa);
> >
> > Why not pass &fsxat.fsx directly to vfs_fileattr_set?
> >
> > > + mnt_drop_write(filepath.mnt);
> > > + path_put(&filepath);
> > > + return error;
> > > +}
> > > +
> > > static int ioctl_getfsuuid(struct file *file, void __user *argp)
> > > {
> > > struct super_block *sb = file_inode(file)->i_sb;
> > > @@ -872,6 +959,12 @@ static int do_vfs_ioctl(struct file *filp, unsigned int fd,
> > > case FS_IOC_FSSETXATTR:
> > > return ioctl_fssetxattr(filp, argp);
> > >
> > > + case FS_IOC_FSGETXATTRAT:
> > > + return ioctl_fsgetxattrat(filp, argp);
> > > +
> > > + case FS_IOC_FSSETXATTRAT:
> > > + return ioctl_fssetxattrat(filp, argp);
> > > +
> > > case FS_IOC_GETFSUUID:
> > > return ioctl_getfsuuid(filp, argp);
> > >
> > > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> > > index 45e4e64fd664..f8cd8d7bf35d 100644
> > > --- a/include/uapi/linux/fs.h
> > > +++ b/include/uapi/linux/fs.h
> > > @@ -139,6 +139,15 @@ struct fsxattr {
> > > unsigned char fsx_pad[8];
> > > };
> > >
> > > +/*
> > > + * Structure passed to FS_IOC_FSGETXATTRAT/FS_IOC_FSSETXATTRAT
> > > + */
> > > +struct fsxattrat {
> > > + struct fsxattr fsx; /* XATTR to get/set */
> > > + __u32 dfd; /* parent dir */
> > > + const char __user *path;
> >
> > As I mentioned last time[1], embedding a pointer in an ioctl structure
> > creates porting problems because pointer sizes vary between process
> > personalities, so the size of struct fsxattrat will vary and lead to
> > copy_to/from_user overflows.
> >
> >
> > [1] https://lore.kernel.org/linux-xfs/20240509232517.GR360919@frogsfrogsfrogs/
>
> So as you've mentioned in that thread using a u64 or here an aligned_u64
> makes the most sense. The kernel has all the necessary magic to deal
> with this already (u64_to_user_ptr() helper etc.). If you want to be
> extra-sure it's possible to slap a size for that path as well.
>
> The ioctl structure can be versioned by size if it's 64bit aligned. The
> ioctl code encodes the size of the struct and since the current
> structure is all nicely 64bit aligned it should just work (tm).
>
> kernel/seccomp.c does that size verisioning by ioctl as an example. Then
> one can do:
>
> #define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK))
>
> switch (EA_IOCTL(cmd)) {
> case EA_IOCTL(FS_IOC_FSGETXATTRAT):
> ret = copy_struct_from_user(&kstruct, sizeof(kstruct), usstruct, _IOC_SIZE(cmd));
>
> Which will do all the heavy lifting for you. To me that seems
> workable but I might miss other problems you're thinking of.
Resending with fixed fsdevel address...
