Re: double kernel page table entry for the same physical page?!
From: ming lei <hidden>
Date: 2005-07-14 01:57:05
Dan, No one intents to make memory corruption in kernel space but it happens sometimes. Say I have a global var in my kernel module which called test-mod, it picks up a physical page allocated by some code with kmalloc and later kfreed(suppose when it does, the whole page gets freed). But then this code forgets a pointer(which maped to this physical page) already freed and modifies the pointer, the write gets thru since that virt address's PTE still valid and points to the physical page currently used by test-mod. So the memory corruption happens. Maybe I miss something in the linux kernel code that prevents this double PTE thing. Ming
--- Dan Malek <dan@embeddededge.com> wrote:
On Jul 13, 2005, at 2:48 PM, ming lei wrote:quoted
Why linux kernel does such thing and no oneconsiderquoted
it's a problem?Because we don't write software that accesses the memory from both of those locations, unless it is very intentional and necessary. If you are just fishing for ways software _could_ do bad things, there are tons of them. It's our job to write it so it doesn't :-) Thanks. -- Dan
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