@@ -955,26 +955,23 @@ static bool safe_hardlink_source(struct inode *inode)
* - sysctl_protected_hardlinks enabled
* - fsuid does not match inode
* - hardlink source is unsafe (see safe_hardlink_source() above)
- * - not CAP_FOWNER
+ * - not CAP_FOWNER in a namespace with the inode owner uid mapped
*
* Returns 0 if successful, -ve on error.
*/
static int may_linkat(struct path *link)
{
- const struct cred *cred;
struct inode *inode;
if (!sysctl_protected_hardlinks)
return 0;
- cred = current_cred();
inode = link->dentry->d_inode;
/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
* otherwise, it must be a safe source.
*/
- if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
- capable(CAP_FOWNER))
+ if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
return 0;
audit_log_link_denied("linkat", link);
Attempting to hardlink to an unsafe file (e.g. a setuid binary) from within an unprivileged user namespace fails, even if CAP_FOWNER is held within the namespace. This may cause various failures, such as a gentoo installation within a lxc container failing to build and install specific packages. This change permits hardlinking of files owned by mapped uids, if CAP_FOWNER is held for that namespace. Furthermore, it improves consistency by using the existing inode_owner_or_capable(), which is aware of namespaced capabilities as of 23adbe12ef7d3 ("fs,userns: Change inode_capable to capable_wrt_inode_uidgid"). Signed-off-by: Dirk Steinmetz <public@rsjtdrjgfuzkfg.com> --- fs/namei.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)