releases/5.0.14/x86-mm-fix-a-crash-with-kmemleak_scan.patch

   1 From 0d02113b31b2017dd349ec9df2314e798a90fa6e Mon Sep 17 00:00:00 2001
   2 From: Qian Cai <cai@lca.pw>
   3 Date: Tue, 23 Apr 2019 12:58:11 -0400
   4 Subject: x86/mm: Fix a crash with kmemleak_scan()
   5
   6 From: Qian Cai <cai@lca.pw>
   7
   8 commit 0d02113b31b2017dd349ec9df2314e798a90fa6e upstream.
   9
  10 The first kmemleak_scan() call after boot would trigger the crash below
  11 because this callpath:
  12
  13   kernel_init
  14     free_initmem
  15       mem_encrypt_free_decrypted_mem
  16         free_init_pages
  17
  18 unmaps memory inside the .bss when DEBUG_PAGEALLOC=y.
  19
  20 kmemleak_init() will register the .data/.bss sections and then
  21 kmemleak_scan() will scan those addresses and dereference them looking
  22 for pointer references. If free_init_pages() frees and unmaps pages in
  23 those sections, kmemleak_scan() will crash if referencing one of those
  24 addresses:
  25
  26   BUG: unable to handle kernel paging request at ffffffffbd402000
  27   CPU: 12 PID: 325 Comm: kmemleak Not tainted 5.1.0-rc4+ #4
  28   RIP: 0010:scan_block
  29   Call Trace:
  30    scan_gray_list
  31    kmemleak_scan
  32    kmemleak_scan_thread
  33    kthread
  34    ret_from_fork
  35
  36 Since kmemleak_free_part() is tolerant to unknown objects (not tracked
  37 by kmemleak), it is fine to call it from free_init_pages() even if not
  38 all address ranges passed to this function are known to kmemleak.
  39
  40  [ bp: Massage. ]
  41
  42 Fixes: b3f0907c71e0 ("x86/mm: Add .bss..decrypted section to hold shared variables")
  43 Signed-off-by: Qian Cai <cai@lca.pw>
  44 Signed-off-by: Borislav Petkov <bp@suse.de>
  45 Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
  46 Cc: Andy Lutomirski <luto@kernel.org>
  47 Cc: Brijesh Singh <brijesh.singh@amd.com>
  48 Cc: Dave Hansen <dave.hansen@linux.intel.com>
  49 Cc: "H. Peter Anvin" <hpa@zytor.com>
  50 Cc: Ingo Molnar <mingo@redhat.com>
  51 Cc: Peter Zijlstra <peterz@infradead.org>
  52 Cc: Thomas Gleixner <tglx@linutronix.de>
  53 Cc: x86-ml <x86@kernel.org>
  54 Link: https://lkml.kernel.org/r/20190423165811.36699-1-cai@lca.pw
  55 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  56
  57 ---
  58  arch/x86/mm/init.c |    6 ++++++
  59  1 file changed, 6 insertions(+)
  60
  61 --- a/arch/x86/mm/init.c
  62 +++ b/arch/x86/mm/init.c
  63 @@ -5,6 +5,7 @@
  64  #include <linux/memblock.h>
  65  #include <linux/swapfile.h>
  66  #include <linux/swapops.h>
  67 +#include <linux/kmemleak.h>
  68
  69  #include <asm/set_memory.h>
  70  #include <asm/e820/api.h>
  71 @@ -766,6 +767,11 @@ void free_init_pages(const char *what, u
  72         if (debug_pagealloc_enabled()) {
  73                 pr_info("debug: unmapping init [mem %#010lx-%#010lx]\n",
  74                         begin, end - 1);
  75 +               /*
  76 +                * Inform kmemleak about the hole in the memory since the
  77 +                * corresponding pages will be unmapped.
  78 +                */
  79 +               kmemleak_free_part((void *)begin, end - begin);
  80                 set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
  81         } else {
  82                 /*