Now that all the plumbing is in place, switch over to using the new inode operations to get/set fs caps. This pushes all mapping of ids into the caller's user ns to above the vfs_*() level, making this consistent with other vfs_*() interfaces.
cap_convert_nscap() is updated to return vfs_caps and moved to be called from the new code path for setting fscaps. This means that use of vfs_setxattr() will no longer remap ids in fscap xattrs, but all code which used vfs_setxattr() for fscaps xattrs has been converted to the new interfaces. Removing the mapping of fscaps rootids from vfs_getxattr() is more invovled and will be addressed in a later commit. Signed-off-by: Seth Forshee (DigitalOcean) <[email protected]> --- fs/xattr.c | 49 ++++++++++++++++++++++++---- include/linux/capability.h | 2 +- security/commoncap.c | 79 +++++++++++++++------------------------------- 3 files changed, 69 insertions(+), 61 deletions(-) diff --git a/fs/xattr.c b/fs/xattr.c index 8b0f7384cbc9..30eff6bc4f6d 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -534,13 +534,6 @@ vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, const void *orig_value = value; int error; - if (size && is_fscaps_xattr(name)) { - error = cap_convert_nscap(idmap, dentry, &value, size); - if (error < 0) - return error; - size = error; - } - retry_deleg: inode_lock(inode); error = __vfs_setxattr_locked(idmap, dentry, name, value, size, @@ -851,6 +844,24 @@ int do_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, return do_set_acl(idmap, dentry, ctx->kname->name, ctx->kvalue, ctx->size); + if (is_fscaps_xattr(ctx->kname->name)) { + struct vfs_caps caps; + int ret; + + /* + * rootid is already in the mount idmap, so pass nop_mnt_idmap + * so that it won't be mapped. + */ + ret = vfs_caps_from_xattr(&nop_mnt_idmap, current_user_ns(), + &caps, ctx->kvalue, ctx->size); + if (ret) + return ret; + ret = cap_convert_nscap(idmap, dentry, &caps); + if (ret) + return ret; + return vfs_set_fscaps(idmap, dentry, &caps, ctx->flags); + } + return vfs_setxattr(idmap, dentry, ctx->kname->name, ctx->kvalue, ctx->size, ctx->flags); } @@ -949,6 +960,27 @@ do_getxattr(struct mnt_idmap *idmap, struct dentry *d, ssize_t error; char *kname = ctx->kname->name; + if (is_fscaps_xattr(kname)) { + struct vfs_caps caps; + struct vfs_ns_cap_data data; + int ret; + + ret = vfs_get_fscaps(idmap, d, &caps); + if (ret) + return ret; + /* + * rootid is already in the mount idmap, so pass nop_mnt_idmap + * so that it won't be mapped. + */ + ret = vfs_caps_to_user_xattr(&nop_mnt_idmap, current_user_ns(), + &caps, &data, ctx->size); + if (ret < 0) + return ret; + if (ctx->size && copy_to_user(ctx->value, &data, ret)) + return -EFAULT; + return ret; + } + if (ctx->size) { if (ctx->size > XATTR_SIZE_MAX) ctx->size = XATTR_SIZE_MAX; @@ -1139,6 +1171,9 @@ removexattr(struct mnt_idmap *idmap, struct dentry *d, if (is_posix_acl_xattr(kname)) return vfs_remove_acl(idmap, d, kname); + if (is_fscaps_xattr(kname)) + return vfs_remove_fscaps(idmap, d); + return vfs_removexattr(idmap, d, kname); } diff --git a/include/linux/capability.h b/include/linux/capability.h index eb06d7c6224b..5e7cbf07e3a7 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -229,6 +229,6 @@ int get_vfs_caps_from_disk(struct mnt_idmap *idmap, struct vfs_caps *cpu_caps); int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry, - const void **ivalue, size_t size); + struct vfs_caps *caps); #endif /* !_LINUX_CAPABILITY_H */ diff --git a/security/commoncap.c b/security/commoncap.c index 19affcfa3126..4254e5e46024 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -485,27 +485,21 @@ int cap_inode_getsecurity(struct mnt_idmap *idmap, } /** - * rootid_from_xattr - translate root uid of vfs caps + * rootid_from_vfs_caps - translate root uid of vfs caps * - * @value: vfs caps value which may be modified by this function - * @size: size of @ivalue + * @caps: vfs caps value which may be modified by this function * @task_ns: user namespace of the caller + * + * Return the rootid from a v3 fs cap, or the id of root in the task's user + * namespace for v1 and v2 fs caps. */ -static vfsuid_t rootid_from_xattr(const void *value, size_t size, - struct user_namespace *task_ns) +static vfsuid_t rootid_from_vfs_caps(const struct vfs_caps *caps, + struct user_namespace *task_ns) { - const struct vfs_ns_cap_data *nscap = value; - uid_t rootid = 0; - - if (size == XATTR_CAPS_SZ_3) - rootid = le32_to_cpu(nscap->rootid); - - return VFSUIDT_INIT(make_kuid(task_ns, rootid)); -} + if ((caps->magic_etc & VFS_CAP_REVISION_MASK) == VFS_CAP_REVISION_3) + return caps->rootid; -static bool validheader(size_t size, const struct vfs_cap_data *cap) -{ - return is_v2header(size, cap) || is_v3header(size, cap); + return VFSUIDT_INIT(make_kuid(task_ns, 0)); } /** @@ -513,11 +507,10 @@ static bool validheader(size_t size, const struct vfs_cap_data *cap) * * @idmap: idmap of the mount the inode was found from * @dentry: used to retrieve inode to check permissions on - * @ivalue: vfs caps value which may be modified by this function - * @size: size of @ivalue + * @caps: vfs caps which may be modified by this function * - * User requested a write of security.capability. If needed, update the - * xattr to change from v2 to v3, or to fixup the v3 rootid. + * User requested a write of security.capability. Check permissions, and if + * needed, update the xattr to change from v2 to v3. * * If the inode has been found through an idmapped mount the idmap of * the vfsmount must be passed through @idmap. This function will then @@ -525,59 +518,39 @@ static bool validheader(size_t size, const struct vfs_cap_data *cap) * permissions. On non-idmapped mounts or if permission checking is to be * performed on the raw inode simply pass @nop_mnt_idmap. * - * Return: On success, return the new size; on error, return < 0. + * Return: On success, return 0; on error, return < 0. */ int cap_convert_nscap(struct mnt_idmap *idmap, struct dentry *dentry, - const void **ivalue, size_t size) + struct vfs_caps *caps) { - struct vfs_ns_cap_data *nscap; - uid_t nsrootid; - const struct vfs_cap_data *cap = *ivalue; - __u32 magic, nsmagic; struct inode *inode = d_backing_inode(dentry); struct user_namespace *task_ns = current_user_ns(), *fs_ns = inode->i_sb->s_user_ns; - kuid_t rootid; vfsuid_t vfsrootid; - size_t newsize; + __u32 revision; - if (!*ivalue) - return -EINVAL; - if (!validheader(size, cap)) + revision = sansflags(caps->magic_etc); + if (revision != VFS_CAP_REVISION_2 && revision != VFS_CAP_REVISION_3) return -EINVAL; if (!capable_wrt_inode_uidgid(idmap, inode, CAP_SETFCAP)) return -EPERM; - if (size == XATTR_CAPS_SZ_2 && (idmap == &nop_mnt_idmap)) + if (revision == VFS_CAP_REVISION_2 && (idmap == &nop_mnt_idmap)) if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP)) /* user is privileged, just write the v2 */ - return size; + return 0; - vfsrootid = rootid_from_xattr(*ivalue, size, task_ns); + vfsrootid = rootid_from_vfs_caps(caps, task_ns); if (!vfsuid_valid(vfsrootid)) return -EINVAL; - rootid = from_vfsuid(idmap, fs_ns, vfsrootid); - if (!uid_valid(rootid)) + if (!vfsuid_has_fsmapping(idmap, fs_ns, vfsrootid)) return -EINVAL; - nsrootid = from_kuid(fs_ns, rootid); - if (nsrootid == -1) - return -EINVAL; + caps->rootid = vfsrootid; + caps->magic_etc = VFS_CAP_REVISION_3 | + (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE); - newsize = sizeof(struct vfs_ns_cap_data); - nscap = kmalloc(newsize, GFP_ATOMIC); - if (!nscap) - return -ENOMEM; - nscap->rootid = cpu_to_le32(nsrootid); - nsmagic = VFS_CAP_REVISION_3; - magic = le32_to_cpu(cap->magic_etc); - if (magic & VFS_CAP_FLAGS_EFFECTIVE) - nsmagic |= VFS_CAP_FLAGS_EFFECTIVE; - nscap->magic_etc = cpu_to_le32(nsmagic); - memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32); - - *ivalue = nscap; - return newsize; + return 0; } /* -- 2.43.0
