• Glauber Costa's avatar
    fork: protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs · 2ad306b1
    Glauber Costa authored
    Because those architectures will draw their stacks directly from the page
    allocator, rather than the slab cache, we can directly pass __GFP_KMEMCG
    flag, and issue the corresponding free_pages.
    
    This code path is taken when the architecture doesn't define
    CONFIG_ARCH_THREAD_INFO_ALLOCATOR (only ia64 seems to), and has
    THREAD_SIZE >= PAGE_SIZE.  Luckily, most - if not all - of the remaining
    architectures fall in this category.
    
    This will guarantee that every stack page is accounted to the memcg the
    process currently lives on, and will have the allocations to fail if they
    go over limit.
    
    For the time being, I am defining a new variant of THREADINFO_GFP, not to
    mess with the other path.  Once the slab is also tracked by memcg, we can
    get rid of that flag.
    
    Tested to successfully protect against :(){ :|:& };:
    Signed-off-by: default avatarGlauber Costa <glommer@parallels.com>
    Acked-by: default avatarFrederic Weisbecker <fweisbec@redhat.com>
    Acked-by: default avatarKamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Greg Thelen <gthelen@google.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: JoonSoo Kim <js1304@gmail.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Pekka Enberg <penberg@cs.helsinki.fi>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Suleiman Souhlal <suleiman@google.com>
    Cc: Tejun Heo <tj@kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2ad306b1
fork.c 45.2 KB