• Josh Poimboeuf's avatar
    mm/page_alloc: Remove kernel address exposure in free_reserved_area() · 7b95b745
    Josh Poimboeuf authored
    commit adb1fe9a upstream.
    
    Linus suggested we try to remove some of the low-hanging fruit related
    to kernel address exposure in dmesg.  The only leaks I see on my local
    system are:
    
      Freeing SMP alternatives memory: 32K (ffffffff9e309000 - ffffffff9e311000)
      Freeing initrd memory: 10588K (ffffa0b736b42000 - ffffa0b737599000)
      Freeing unused kernel memory: 3592K (ffffffff9df87000 - ffffffff9e309000)
      Freeing unused kernel memory: 1352K (ffffa0b7288ae000 - ffffa0b728a00000)
      Freeing unused kernel memory: 632K (ffffa0b728d62000 - ffffa0b728e00000)
    
    Linus says:
    
      "I suspect we should just remove [the addresses in the 'Freeing'
       messages]. I'm sure they are useful in theory, but I suspect they
       were more useful back when the whole "free init memory" was
       originally done.
    
       These days, if we have a use-after-free, I suspect the init-mem
       situation is the easiest situation by far. Compared to all the dynamic
       allocations which are much more likely to show it anyway. So having
       debug output for that case is likely not all that productive."
    
    With this patch the freeing messages now look like this:
    
      Freeing SMP alternatives memory: 32K
      Freeing initrd memory: 10588K
      Freeing unused kernel memory: 3592K
      Freeing unused kernel memory: 1352K
      Freeing unused kernel memory: 632K
    Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-mm@kvack.org
    Link: http://lkml.kernel.org/r/6836ff90c45b71d38e5d4405aec56fa9e5d1d4b2.1477405374.git.jpoimboe@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    Cc: Kees Cook <keescook@google.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    7b95b745
page_alloc.c 203 KB