On Sat, Mar 29, 2025 at 3:33 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > With getfsxattrat() syscall, filesystem may use this field to report > its supported xflags. Zero mask value means that supported flags are > not advertized. > > With setfsxattrat() syscall, userspace may use this field to declare > which xflags and fields are being set. Zero mask value means that > all known xflags and fields are being set. > > Programs that call getfsxattrat() to fill struct fsxattr before calling > setfsxattrat() will not be affected by this change, but it allows > programs that call setfsxattrat() without calling getfsxattrat() to make > changes to some xflags and fields without knowing or changing the values > of unrelated xflags and fields. > > Link: https://lore.kernel.org/linux-fsdevel/20250216164029.20673-4-pali@xxxxxxxxxx/ > Cc: Pali Rohár <pali@xxxxxxxxxx> > Cc: Andrey Albershteyn <aalbersh@xxxxxxxxxx> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > --- > fs/ioctl.c | 35 +++++++++++++++++++++++++++++------ > include/linux/fileattr.h | 1 + > include/uapi/linux/fs.h | 3 ++- > 3 files changed, 32 insertions(+), 7 deletions(-) > > diff --git a/fs/ioctl.c b/fs/ioctl.c > index b19858db4c432..a4838b3e7de90 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -540,10 +540,13 @@ EXPORT_SYMBOL(vfs_fileattr_get); > > void fileattr_to_fsxattr(const struct fileattr *fa, struct fsxattr *fsx) > { > - __u32 mask = FS_XFALGS_MASK; > + /* Filesystem may or may not advertize supported xflags */ > + __u32 fs_mask = fa->fsx_xflags_mask & FS_XFALGS_MASK; > + __u32 mask = fs_mask ?: FS_XFALGS_MASK; > > memset(fsx, 0, sizeof(struct fsxattr)); > fsx->fsx_xflags = fa->fsx_xflags & mask; > + fsx->fsx_xflags_mask = fs_mask; > fsx->fsx_extsize = fa->fsx_extsize; > fsx->fsx_nextents = fa->fsx_nextents; > fsx->fsx_projid = fa->fsx_projid; > @@ -562,6 +565,8 @@ int copy_fsxattr_to_user(const struct fileattr *fa, struct fsxattr __user *ufa) > struct fsxattr xfa; > > fileattr_to_fsxattr(fa, &xfa); > + /* FS_IOC_FSGETXATTR ioctl does not report supported fsx_xflags_mask */ > + xfa.fsx_xflags_mask = 0; > > if (copy_to_user(ufa, &xfa, sizeof(xfa))) > return -EFAULT; > @@ -572,16 +577,30 @@ EXPORT_SYMBOL(copy_fsxattr_to_user); > > int fsxattr_to_fileattr(const struct fsxattr *fsx, struct fileattr *fa) > { > - __u32 mask = FS_XFALGS_MASK; > + /* User may or may not provide custom xflags mask */ > + __u32 mask = fsx->fsx_xflags_mask ?: FS_XFALGS_MASK; > > - if (fsx->fsx_xflags & ~mask) > + if ((fsx->fsx_xflags & ~mask) || (mask & ~FS_XFALGS_MASK)) > return -EINVAL; > > fileattr_fill_xflags(fa, fsx->fsx_xflags); > fa->fsx_xflags &= ~FS_XFLAG_RDONLY_MASK; > - fa->fsx_extsize = fsx->fsx_extsize; > - fa->fsx_projid = fsx->fsx_projid; > - fa->fsx_cowextsize = fsx->fsx_cowextsize; > + fa->fsx_xflags_mask = fsx->fsx_xflags_mask; > + /* > + * If flags mask is specified, we copy the fields value only if the > + * relevant flag is set in the mask. > + */ > + if (!mask || (mask & (FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT))) > + fa->fsx_extsize = fsx->fsx_extsize; > + if (!mask || (mask & FS_XFLAG_COWEXTSIZE)) > + fa->fsx_cowextsize = fsx->fsx_cowextsize; > + /* > + * To save a mask flag (i.e. FS_XFLAG_PROJID), require setting values > + * of fsx_projid and FS_XFLAG_PROJINHERIT flag values together. > + * For a non-directory, FS_XFLAG_PROJINHERIT flag value should be 0. > + */ > + if (!mask || (mask & FS_XFLAG_PROJINHERIT)) > + fa->fsx_projid = fsx->fsx_projid; Sorry, I ended up initializing the mask without a user provided mask to FS_XFALGS_MASK, so these (!mask ||) conditions are not needed. Thanks, Amir.
