Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

On 2018-02-15 18:34, Paul Moore wrote: > On Wed, Feb 14, 2018 at 11:18 AM, Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > Audit link denied events for symlinks were missing the parent PATH > > record. Add it. Since the full pathname may not be available, > > reconstruct it from the path in the nameidata supplied. > > > > See: https://github.com/linux-audit/audit-kernel/issues/21 > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > > fs/namei.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/fs/namei.c b/fs/namei.c > > index 0edf133..bf1c046b 100644 > > --- a/fs/namei.c > > +++ b/fs/namei.c > > @@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd) > > const struct inode *inode; > > const struct inode *parent; > > kuid_t puid; > > + char *pathname; > > > > if (!sysctl_protected_symlinks) > > return 0; > > @@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd) > > if (nd->flags & LOOKUP_RCU) > > return -ECHILD; > > > > + pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL); > > + if (!pathname) > > + return -ENOMEM; > > + audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname, > > + PATH_MAX + 1)), > > + nd->stack[0].link.dentry, 0); > > Hmm, it's been a while since I've looked at the audit vfs/inode code, > but isn't the audit_inode() call directly above effectively a > duplicate of the audit_inode(nd->name, nd->stack[0].link.dentry, 0) > call you added in patch 3/4? It gets the full pathname string of the link, then converts it to a struct filename*, and then below, we feed it that struct filename* with the parent's dentry and the LOOKUP_PARENT flag to drop the last part of the pathname and set the filetype to PARENT.

I didn't try, it, but I expect if I feed it parent's dentry above, I'd get only the parent pathname and when I feed it to audit_inode() below it would again drop the last part of the pathname when the LOOKUP_PARENT flag is included, or not label it as a filetype PARENT if we don't include the flag to get the full parent pathname. > > + audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT); > > + > > audit_inode(nd->name, nd->stack[0].link.dentry, 0); > > audit_log_link_denied("follow_link", &nd->stack[0].link); > > return -EACCES; > > -- > > 1.8.3.1