Commit bf71bc16 authored May 28, 2020 by Helge Deller

parisc: Fix kernel panic in mem_init()



The Debian kernel v5.6 triggers this kernel panic:

 Kernel panic - not syncing: Bad Address (null pointer deref?)
 Bad Address (null pointer deref?): Code=26 (Data memory access rights trap) at addr 0000000000000000
 CPU: 0 PID: 0 Comm: swapper Not tainted 5.6.0-2-parisc64 #1 Debian 5.6.14-1
  IAOQ[0]: mem_init+0xb0/0x150
  IAOQ[1]: mem_init+0xb4/0x150
  RP(r2): start_kernel+0x6c8/0x1190
 Backtrace:
  [<0000000040101ab4>] start_kernel+0x6c8/0x1190
  [<0000000040108574>] start_parisc+0x158/0x1b8

on a HP-PARISC rp3440 machine with this memory layout:
 Memory Ranges:
  0) Start 0x0000000000000000 End 0x000000003fffffff Size   1024 MB
  1) Start 0x0000004040000000 End 0x00000040ffdfffff Size   3070 MB

Fix the crash by avoiding virt_to_page() and similar functions in
mem_init() until the memory zones have been fully set up.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v5.0+

parent b0c3ba31

arch/parisc/mm/init.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -562,7 +562,7 @@ void __init mem_init(void)
		> BITS_PER_LONG);

		high_memory = __va((max_pfn << PAGE_SHIFT));
		set_max_mapnr(page_to_pfn(virt_to_page(high_memory - 1)) + 1);
		set_max_mapnr(max_low_pfn);
		memblock_free_all();

		#ifdef CONFIG_PA11

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