Two VM problems for the 2.4 TODO list

From: Stephen C. Tweedie (
Date: Mon Sep 04 2000 - 11:07:39 EST

Hi Ted,

To be fixed for 2.4:

1) Non-atomic pte updates

   The page aging code and mprotect both modify existing ptes
   non-atomically. That can stomp on the VM hardware on other CPUs
   setting the dirty bit on mmaped pages when using threads. 2.2 is
   vulnerable too.

2) RSS locking

   swapout holds the page_table_lock while swapping, and adjusts the
   mm->rss while holding that lock. Other places in the mm are not
   so careful about holding the lock, so rss (which is not an
   atomic_t) can be corrupted.


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