Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 28 Sep 2016 16:22:53 -0700 | Subject | Re: [PATCH v2 2/3] mm: add LSM hook for writes to readonly memory |
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On Wed, Sep 28, 2016 at 3:54 PM, Jann Horn <jann@thejh.net> wrote: > SELinux attempts to make it possible to whitelist trustworthy sources of > code that may be mapped into memory, and Android makes use of this feature. > To prevent an attacker from bypassing this by modifying R+X memory through > /proc/$pid/mem or PTRACE_POKETEXT, it is necessary to call a security hook > in check_vma_flags().
If selinux policy allows PTRACE_POKETEXT, is it really so bad for that to result in code execution?
> -struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode) > +struct mm_struct *proc_mem_open(struct inode *inode, > + const struct cred **object_cred, > + unsigned int mode) > {
Why are you passing object_cred all over the place like this? You have an inode, and an inode implies a task.
For that matter, would it possibly make sense to use MEMCG's mm->owner and get rid of object_cred entirely? I can see this causing issues in strange threading cases, e.g. accessing your own /proc/$$/mem vs another thread in your process's.
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