| Message ID | 20240221-idmap-fscap-refactor-v2-19-3039364623bd@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fs: use type-safe uid representation for filesystem capabilities | expand |
On Wed, Feb 21, 2024 at 03:24:50PM -0600, Seth Forshee (DigitalOcean) wrote: > Provide a type-safe interface for removing filesystem capabilities and a > generic implementation suitable for most filesystems. Also add an > internal interface, vfs_remove_fscaps_nosec(), which is called with the > inode lock held and skips security checks for later use from the > capability code. > > Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org> > --- > fs/xattr.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 2 ++ > 2 files changed, 83 insertions(+) > > diff --git a/fs/xattr.c b/fs/xattr.c > index 96de43928a51..8b0f7384cbc9 100644 > --- a/fs/xattr.c > +++ b/fs/xattr.c > @@ -324,6 +324,87 @@ int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > } > EXPORT_SYMBOL(vfs_set_fscaps); > > +static int generic_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) > +{ > + return __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS); > +} > + > +/** > + * vfs_remove_fscaps_nosec - remove filesystem capabilities without > + * security checks > + * @idmap: idmap of the mount the inode was found from > + * @dentry: the dentry from which to remove filesystem capabilities > + * > + * This function removes any filesystem capabilities from the specified > + * dentry. Does not perform any security checks, and callers must hold the > + * inode lock. > + * > + * Return: 0 on success, a negative errno on error. > + */ > +int vfs_remove_fscaps_nosec(struct mnt_idmap *idmap, struct dentry *dentry) > +{ > + struct inode *inode = dentry->d_inode; > + int error; > + > + if (inode->i_op->set_fscaps) > + error = inode->i_op->set_fscaps(idmap, dentry, NULL, > + XATTR_REPLACE); > + else > + error = generic_remove_fscaps(idmap, dentry); > + > + return error; > +} > + > +/** > + * vfs_remove_fscaps - remove filesystem capabilities > + * @idmap: idmap of the mount the inode was found from > + * @dentry: the dentry from which to remove filesystem capabilities > + * > + * This function removes any filesystem capabilities from the specified > + * dentry. > + * > + * Return: 0 on success, a negative errno on error. > + */ > +int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) > +{ > + struct inode *inode = dentry->d_inode; > + struct inode *delegated_inode = NULL; > + int error; > + > +retry_deleg: > + inode_lock(inode); > + > + error = xattr_permission(idmap, inode, XATTR_NAME_CAPS, MAY_WRITE); > + if (error) > + goto out_inode_unlock; Should also use may_write_xattr() instead of xattr_permission() if possible. > + > + error = security_inode_remove_fscaps(idmap, dentry); > + if (error) > + goto out_inode_unlock; > + > + error = try_break_deleg(inode, &delegated_inode); > + if (error) > + goto out_inode_unlock; > + > + error = vfs_remove_fscaps_nosec(idmap, dentry); > + if (!error) { > + fsnotify_xattr(dentry); > + evm_inode_post_remove_fscaps(dentry); > + } > + > +out_inode_unlock: > + inode_unlock(inode); > + > + if (delegated_inode) { > + error = break_deleg_wait(&delegated_inode); > + if (!error) > + goto retry_deleg; > + } > + > + return error; > +} > +EXPORT_SYMBOL(vfs_remove_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 4f5d7ed44644..c07427d2fc71 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2122,6 +2122,8 @@ extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > struct vfs_caps *caps); > extern int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, > const struct vfs_caps *caps, int setxattr_flags); > +extern int vfs_remove_fscaps_nosec(struct mnt_idmap *idmap, struct dentry *dentry); > +extern int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry); Please drop the extern.
diff --git a/fs/xattr.c b/fs/xattr.c index 96de43928a51..8b0f7384cbc9 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -324,6 +324,87 @@ int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, } EXPORT_SYMBOL(vfs_set_fscaps); +static int generic_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) +{ + return __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS); +} + +/** + * vfs_remove_fscaps_nosec - remove filesystem capabilities without + * security checks + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to remove filesystem capabilities + * + * This function removes any filesystem capabilities from the specified + * dentry. Does not perform any security checks, and callers must hold the + * inode lock. + * + * Return: 0 on success, a negative errno on error. + */ +int vfs_remove_fscaps_nosec(struct mnt_idmap *idmap, struct dentry *dentry) +{ + struct inode *inode = dentry->d_inode; + int error; + + if (inode->i_op->set_fscaps) + error = inode->i_op->set_fscaps(idmap, dentry, NULL, + XATTR_REPLACE); + else + error = generic_remove_fscaps(idmap, dentry); + + return error; +} + +/** + * vfs_remove_fscaps - remove filesystem capabilities + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to remove filesystem capabilities + * + * This function removes any filesystem capabilities from the specified + * dentry. + * + * Return: 0 on success, a negative errno on error. + */ +int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) +{ + struct inode *inode = dentry->d_inode; + struct inode *delegated_inode = NULL; + int error; + +retry_deleg: + inode_lock(inode); + + error = xattr_permission(idmap, inode, XATTR_NAME_CAPS, MAY_WRITE); + if (error) + goto out_inode_unlock; + + error = security_inode_remove_fscaps(idmap, dentry); + if (error) + goto out_inode_unlock; + + error = try_break_deleg(inode, &delegated_inode); + if (error) + goto out_inode_unlock; + + error = vfs_remove_fscaps_nosec(idmap, dentry); + if (!error) { + fsnotify_xattr(dentry); + evm_inode_post_remove_fscaps(dentry); + } + +out_inode_unlock: + inode_unlock(inode); + + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + + return error; +} +EXPORT_SYMBOL(vfs_remove_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 4f5d7ed44644..c07427d2fc71 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2122,6 +2122,8 @@ extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, struct vfs_caps *caps); extern int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, const struct vfs_caps *caps, int setxattr_flags); +extern int vfs_remove_fscaps_nosec(struct mnt_idmap *idmap, struct dentry *dentry); +extern int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry); /** * enum freeze_holder - holder of the freeze
Provide a type-safe interface for removing filesystem capabilities and a generic implementation suitable for most filesystems. Also add an internal interface, vfs_remove_fscaps_nosec(), which is called with the inode lock held and skips security checks for later use from the capability code. Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org> --- fs/xattr.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 83 insertions(+)