Commit 0d02113b authored by Qian Cai's avatar Qian Cai Committed by Borislav Petkov

x86/mm: Fix a crash with kmemleak_scan()

The first kmemleak_scan() call after boot would trigger the crash below
because this callpath:

  kernel_init
    free_initmem
      mem_encrypt_free_decrypted_mem
        free_init_pages

unmaps memory inside the .bss when DEBUG_PAGEALLOC=y.

kmemleak_init() will register the .data/.bss sections and then
kmemleak_scan() will scan those addresses and dereference them looking
for pointer references. If free_init_pages() frees and unmaps pages in
those sections, kmemleak_scan() will crash if referencing one of those
addresses:

  BUG: unable to handle kernel paging request at ffffffffbd402000
  CPU: 12 PID: 325 Comm: kmemleak Not tainted 5.1.0-rc4+ #4
  RIP: 0010:scan_block
  Call Trace:
   scan_gray_list
   kmemleak_scan
   kmemleak_scan_thread
   kthread
   ret_from_fork

Since kmemleak_free_part() is tolerant to unknown objects (not tracked
by kmemleak), it is fine to call it from free_init_pages() even if not
all address ranges passed to this function are known to kmemleak.

 [ bp: Massage. ]

Fixes: b3f0907c ("x86/mm: Add .bss..decrypted section to hold shared variables")
Signed-off-by: default avatarQian Cai <cai@lca.pw>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190423165811.36699-1-cai@lca.pw
parent 36f0c423
......@@ -5,6 +5,7 @@
#include <linux/memblock.h>
#include <linux/swapfile.h>
#include <linux/swapops.h>
#include <linux/kmemleak.h>
#include <asm/set_memory.h>
#include <asm/e820/api.h>
......@@ -766,6 +767,11 @@ void free_init_pages(const char *what, unsigned long begin, unsigned long end)
if (debug_pagealloc_enabled()) {
pr_info("debug: unmapping init [mem %#010lx-%#010lx]\n",
begin, end - 1);
/*
* Inform kmemleak about the hole in the memory since the
* corresponding pages will be unmapped.
*/
kmemleak_free_part((void *)begin, end - begin);
set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
} else {
/*
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment