On 15.10.2013 08:40, Ingo Molnar wrote:
* Frederic Weisbecker <fweis...@gmail.com> wrote:
I've been thinking that CONFIG_DEBUG_LIST could help. Unfortunately it's
good to spot list APIs misuse but, if Linus is right, the problem may be
that the list belongs to an object that has been freed, and I believe
that won't detect such a thing.
Use-after free should be reliably detectable via CONFIG_DEBUG_PAGEALLOC=y.
Enabled.
Hmm ... I think i spotted a KConfig bug. In mm/Kconfig.debug I read:
config DEBUG_PAGEALLOC
bool "Debug page memory allocations"
depends on DEBUG_KERNEL
depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC &&
!SPARC
depends on !KMEMCHECK
select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
select PAGE_GUARD if ARCH_SUPPORTS_DEBUG_PAGEALLOC
---help---
Unmap pages from the kernel linear mapping after free_pages().
This results in a large slowdown, but helps to find certain types
of memory corruption.
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify
the patterns before alloc_pages(). Additionally,
this option cannot be enabled in combination with hibernation as
that would result in incorrect warnings of memory corruption after
a resume because free pages are not saved to the suspend image.
Either the description or the "depends" line that includes !HIBERNATION is
wrong. Maybe
depends on DEBUG_KERNEL
- depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC &&
!SPARC
+ depends on !HIBERNATION && ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC &&
!SPARC
depends on !KMEMCHECK
is correct, at least does not allow HIBERNATION and DEBUG_PAGEALLOC to be
enabled simultaneously.
A couple of years ago I wrote a list debugging beast that would catch
use-after-free mishaps (sent it to lkml too IIRC), but it was a bit
complex and I never found the time to nurse it upstream.
Thanks,
Ingo
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