| Message ID | 20231129-idmap-fscap-refactor-v1-8-da5a26058a5b@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fs: use type-safe uid representation for filesystem capabilities | expand |
On Wed, Nov 29, 2023 at 03:50:26PM -0600, Seth Forshee (DigitalOcean) wrote: > Provide a type-safe interface for retrieving filesystem capabilities and > a generic implementation suitable for most filesystems. Also add an > internal interface, __vfs_get_fscaps(), which skips security checks for > later use from the capability code. > > Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org> > --- > fs/xattr.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 4 ++++ > 2 files changed, 70 insertions(+) > > diff --git a/fs/xattr.c b/fs/xattr.c > index 09d927603433..3abaf9bef0a5 100644 > --- a/fs/xattr.c > +++ b/fs/xattr.c > @@ -181,6 +181,72 @@ xattr_supports_user_prefix(struct inode *inode) > } > EXPORT_SYMBOL(xattr_supports_user_prefix); > > +static int generic_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > + struct vfs_caps *caps) > +{ > + struct inode *inode = d_inode(dentry); > + struct vfs_ns_cap_data *nscaps = NULL; > + int ret; > + > + ret = (int)vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, I don't think you need that case here. > + (char **)&nscaps, 0, GFP_NOFS); > + > + if (ret >= 0) > + ret = vfs_caps_from_xattr(idmap, i_user_ns(inode), caps, nscaps, ret); > + > + kfree(nscaps); > + return ret; > +} > + > +/** > + * __vfs_get_fscaps - get filesystem capabilities without security checks > + * @idmap: idmap of the mount the inode was found from > + * @dentry: the dentry from which to get filesystem capabilities > + * @caps: storage in which to return the filesystem capabilities > + * > + * This function gets the filesystem capabilities for the dentry and returns > + * them in @caps. It does not perform security checks. > + * > + * Return: 0 on success, a negative errno on error. > + */ > +int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > + struct vfs_caps *caps) I would rename that to vfs_get_fscaps_nosec(). We do that for vfs_getxattr_nosec() as well. It's not pretty but it's better than just slapping underscores onto it imo.
On Fri, Dec 01, 2023 at 06:09:36PM +0100, Christian Brauner wrote: > On Wed, Nov 29, 2023 at 03:50:26PM -0600, Seth Forshee (DigitalOcean) wrote: > > Provide a type-safe interface for retrieving filesystem capabilities and > > a generic implementation suitable for most filesystems. Also add an > > internal interface, __vfs_get_fscaps(), which skips security checks for > > later use from the capability code. > > > > Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org> > > --- > > fs/xattr.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/fs.h | 4 ++++ > > 2 files changed, 70 insertions(+) > > > > diff --git a/fs/xattr.c b/fs/xattr.c > > index 09d927603433..3abaf9bef0a5 100644 > > --- a/fs/xattr.c > > +++ b/fs/xattr.c > > @@ -181,6 +181,72 @@ xattr_supports_user_prefix(struct inode *inode) > > } > > EXPORT_SYMBOL(xattr_supports_user_prefix); > > > > +static int generic_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > > + struct vfs_caps *caps) > > +{ > > + struct inode *inode = d_inode(dentry); > > + struct vfs_ns_cap_data *nscaps = NULL; > > + int ret; > > + > > + ret = (int)vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, > > I don't think you need that case here. Yep. I played with a few different implementations of this function, so I'm guessing I did need it at one point and failed to notice when it was no longer needed. > > > + (char **)&nscaps, 0, GFP_NOFS); > > + > > + if (ret >= 0) > > + ret = vfs_caps_from_xattr(idmap, i_user_ns(inode), caps, nscaps, ret); > > + > > + kfree(nscaps); > > + return ret; > > +} > > + > > +/** > > + * __vfs_get_fscaps - get filesystem capabilities without security checks > > + * @idmap: idmap of the mount the inode was found from > > + * @dentry: the dentry from which to get filesystem capabilities > > + * @caps: storage in which to return the filesystem capabilities > > + * > > + * This function gets the filesystem capabilities for the dentry and returns > > + * them in @caps. It does not perform security checks. > > + * > > + * Return: 0 on success, a negative errno on error. > > + */ > > +int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > > + struct vfs_caps *caps) > > I would rename that to vfs_get_fscaps_nosec(). We do that for > vfs_getxattr_nosec() as well. It's not pretty but it's better than just > slapping underscores onto it imo. Will do.
diff --git a/fs/xattr.c b/fs/xattr.c index 09d927603433..3abaf9bef0a5 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -181,6 +181,72 @@ xattr_supports_user_prefix(struct inode *inode) } EXPORT_SYMBOL(xattr_supports_user_prefix); +static int generic_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + struct vfs_caps *caps) +{ + struct inode *inode = d_inode(dentry); + struct vfs_ns_cap_data *nscaps = NULL; + int ret; + + ret = (int)vfs_getxattr_alloc(idmap, dentry, XATTR_NAME_CAPS, + (char **)&nscaps, 0, GFP_NOFS); + + if (ret >= 0) + ret = vfs_caps_from_xattr(idmap, i_user_ns(inode), caps, nscaps, ret); + + kfree(nscaps); + return ret; +} + +/** + * __vfs_get_fscaps - get filesystem capabilities without security checks + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to get filesystem capabilities + * @caps: storage in which to return the filesystem capabilities + * + * This function gets the filesystem capabilities for the dentry and returns + * them in @caps. It does not perform security checks. + * + * Return: 0 on success, a negative errno on error. + */ +int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + struct vfs_caps *caps) +{ + struct inode *inode = d_inode(dentry); + + if (inode->i_op->get_fscaps) + return inode->i_op->get_fscaps(idmap, dentry, caps); + return generic_get_fscaps(idmap, dentry, caps); +} + +/** + * vfs_get_fscaps - get filesystem capabilities + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to get filesystem capabilities + * @caps: storage in which to return the filesystem capabilities + * + * This function gets the filesystem capabilities for the dentry and returns + * them in @caps. + * + * Return: 0 on success, a negative errno on error. + */ +int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + struct vfs_caps *caps) +{ + int error; + + /* + * The VFS has no restrictions on reading security.* xattrs, so + * xattr_permission() isn't needed. Only LSMs get a say. + */ + error = security_inode_getxattr(dentry, XATTR_NAME_CAPS); + if (error) + return error; + + return __vfs_get_fscaps(idmap, dentry, caps); +} +EXPORT_SYMBOL(vfs_get_fscaps); + int __vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, struct inode *inode, const char *name, const void *value, diff --git a/include/linux/fs.h b/include/linux/fs.h index a0a77f67b999..e25b39e4017a 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2055,6 +2055,10 @@ extern int vfs_dedupe_file_range(struct file *file, extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos, struct file *dst_file, loff_t dst_pos, loff_t len, unsigned int remap_flags); +extern int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + struct vfs_caps *caps); +extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + struct vfs_caps *caps); enum freeze_holder { FREEZE_HOLDER_KERNEL = (1U << 0),
Provide a type-safe interface for retrieving filesystem capabilities and a generic implementation suitable for most filesystems. Also add an internal interface, __vfs_get_fscaps(), which skips security checks for later use from the capability code. Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org> --- fs/xattr.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 4 ++++ 2 files changed, 70 insertions(+)