| Message ID | 156022840560.3227213.4776913678782966728.stgit@magnolia (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | vfs: make immutable files actually immutable | expand |
On Mon 10-06-19 21:46:45, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@oracle.com> > > The chattr manpage has this to say about immutable files: > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > or renamed, no link can be created to this file, most of the file's > metadata can not be modified, and the file can not be opened in write > mode." > > However, we don't actually check the immutable flag in the setattr code, > which means that we can update inode flags and project ids and extent > size hints on supposedly immutable files. Therefore, reject setflags > and fssetxattr calls on an immutable file if the file is immutable and > will remain that way. > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > --- > fs/inode.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > > diff --git a/fs/inode.c b/fs/inode.c > index a3757051fd55..adfb458bf533 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -2184,6 +2184,17 @@ int vfs_ioc_setflags_check(struct inode *inode, int oldflags, int flags) > !capable(CAP_LINUX_IMMUTABLE)) > return -EPERM; > > + /* > + * We aren't allowed to change any other flags if the immutable flag is > + * already set and is not being unset. > + */ > + if ((oldflags & FS_IMMUTABLE_FL) && > + (flags & FS_IMMUTABLE_FL)) { > + if ((oldflags & ~FS_IMMUTABLE_FL) != > + (flags & ~FS_IMMUTABLE_FL)) This check looks a bit strange when you've just check FS_IMMUTABLE_FL isn't changing... Why not just oldflags != flags? > + if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) { > + if ((old_fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE) != > + (fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE)) Ditto here... > + return -EPERM; > + if (old_fa->fsx_projid != fa->fsx_projid) > + return -EPERM; > + if ((fa->fsx_xflags & (FS_XFLAG_EXTSIZE | > + FS_XFLAG_EXTSZINHERIT)) && > + old_fa->fsx_extsize != fa->fsx_extsize) > + return -EPERM; > + if ((old_fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) && > + old_fa->fsx_cowextsize != fa->fsx_cowextsize) > + return -EPERM; > + } > + > /* Extent size hints of zero turn off the flags. */ > if (fa->fsx_extsize == 0) > fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT); Honza
On Thu, Jun 20, 2019 at 04:03:45PM +0200, Jan Kara wrote: > On Mon 10-06-19 21:46:45, Darrick J. Wong wrote: > > From: Darrick J. Wong <darrick.wong@oracle.com> > > > > The chattr manpage has this to say about immutable files: > > > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > > or renamed, no link can be created to this file, most of the file's > > metadata can not be modified, and the file can not be opened in write > > mode." > > > > However, we don't actually check the immutable flag in the setattr code, > > which means that we can update inode flags and project ids and extent > > size hints on supposedly immutable files. Therefore, reject setflags > > and fssetxattr calls on an immutable file if the file is immutable and > > will remain that way. > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > > --- > > fs/inode.c | 31 +++++++++++++++++++++++++++++++ > > 1 file changed, 31 insertions(+) > > > > > > diff --git a/fs/inode.c b/fs/inode.c > > index a3757051fd55..adfb458bf533 100644 > > --- a/fs/inode.c > > +++ b/fs/inode.c > > @@ -2184,6 +2184,17 @@ int vfs_ioc_setflags_check(struct inode *inode, int oldflags, int flags) > > !capable(CAP_LINUX_IMMUTABLE)) > > return -EPERM; > > > > + /* > > + * We aren't allowed to change any other flags if the immutable flag is > > + * already set and is not being unset. > > + */ > > + if ((oldflags & FS_IMMUTABLE_FL) && > > + (flags & FS_IMMUTABLE_FL)) { > > + if ((oldflags & ~FS_IMMUTABLE_FL) != > > + (flags & ~FS_IMMUTABLE_FL)) > > This check looks a bit strange when you've just check FS_IMMUTABLE_FL isn't > changing... Why not just oldflags != flags? > > > + if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && > > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) { > > + if ((old_fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE) != > > + (fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE)) > > Ditto here... Good point! I'll fix it. --D > > > + return -EPERM; > > + if (old_fa->fsx_projid != fa->fsx_projid) > > + return -EPERM; > > + if ((fa->fsx_xflags & (FS_XFLAG_EXTSIZE | > > + FS_XFLAG_EXTSZINHERIT)) && > > + old_fa->fsx_extsize != fa->fsx_extsize) > > + return -EPERM; > > + if ((old_fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) && > > + old_fa->fsx_cowextsize != fa->fsx_cowextsize) > > + return -EPERM; > > + } > > + > > /* Extent size hints of zero turn off the flags. */ > > if (fa->fsx_extsize == 0) > > fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT); > > Honza > -- > Jan Kara <jack@suse.com> > SUSE Labs, CR
diff --git a/fs/inode.c b/fs/inode.c index a3757051fd55..adfb458bf533 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2184,6 +2184,17 @@ int vfs_ioc_setflags_check(struct inode *inode, int oldflags, int flags) !capable(CAP_LINUX_IMMUTABLE)) return -EPERM; + /* + * We aren't allowed to change any other flags if the immutable flag is + * already set and is not being unset. + */ + if ((oldflags & FS_IMMUTABLE_FL) && + (flags & FS_IMMUTABLE_FL)) { + if ((oldflags & ~FS_IMMUTABLE_FL) != + (flags & ~FS_IMMUTABLE_FL)) + return -EPERM; + } + return 0; } EXPORT_SYMBOL(vfs_ioc_setflags_check); @@ -2226,6 +2237,26 @@ int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa, !S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode)) return -EINVAL; + /* + * We aren't allowed to change any fields if the immutable flag is + * already set and is not being unset. + */ + if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) && + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) { + if ((old_fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE) != + (fa->fsx_xflags & ~FS_XFLAG_IMMUTABLE)) + return -EPERM; + if (old_fa->fsx_projid != fa->fsx_projid) + return -EPERM; + if ((fa->fsx_xflags & (FS_XFLAG_EXTSIZE | + FS_XFLAG_EXTSZINHERIT)) && + old_fa->fsx_extsize != fa->fsx_extsize) + return -EPERM; + if ((old_fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) && + old_fa->fsx_cowextsize != fa->fsx_cowextsize) + return -EPERM; + } + /* Extent size hints of zero turn off the flags. */ if (fa->fsx_extsize == 0) fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT);