Re: [PATCH 1/1] uprobes: Fix the memory out of bound overwrite in copy_insn()

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

* Oleg Nesterov <oleg@redhat.com> [2013-11-07 20:40:32]:

> 1. copy_insn() doesn't look very nice, all calculations are
>    confusing and it is not immediately clear why do we read
>    the 2nd page first.
> 
> 2. The usage of inode->i_size is wrong on 32-bit machines.
> 
> 3. "Instruction at end of binary" logic is simply wrong, it
>    doesn't handle the case when uprobe->offset > inode->i_size.
> 
>    In this case "bytes" overflows, and __copy_insn() writes to
>    the memory outside of uprobe->arch.insn.
> 
>    Yes, uprobe_register() checks i_size_read(), but this file
>    can be truncated after that. All i_size checks are racy, we
>    do this only to catch the obvious mistakes.
> 
> Change copy_insn() to call __copy_insn() in a loop, simplify
> and fix the bytes/nbytes calculations.
> 
> Note: we do not care if offset + size > i_size, the users of
> arch_uprobe->insn can't know how many bytes were actually copied
> anyway. But perhaps this needs more changes.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

-- 
Thanks and Regards
Srikar Dronamraju