Re: mm: NULL ptr deref in remove_migration_pte

[Christoph Lameter]

On Mon, 16 Jun 2014, Sasha Levin wrote:

> It took some time to hit something here, but I think that the following
> is related:

This related thing looks like someone did a random memset. The SLUB
diagnostic show the object, redzone and padding were overwritten with
zeros.

> [  494.710068] =============================================================================
> [  494.710068] BUG page->ptl (Not tainted): Redzone overwritten
> [  494.710068] -----------------------------------------------------------------------------
> [  494.710068]
> [  494.710068] INFO: 0xffff8804e4730e58-0xffff8804e4730e5f. First byte 0x0 instead of 0xbb
> [  494.710068] INFO: Slab 0xffffea001391cc00 objects=40 used=40 fp=0x          (null) flags=0x56fffff80004080
> [  494.710068] INFO: Object 0xffff8804e4730e10 @offset=3600 fp=0x          (null)
> [  494.710068]
> [  494.710068] Bytes b4 ffff8804e4730e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  494.710068] Object ffff8804e4730e10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  494.710068] Object ffff8804e4730e20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  494.710068] Object ffff8804e4730e30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  494.710068] Object ffff8804e4730e40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [  494.710068] Object ffff8804e4730e50: 00 00 00 00 00 00 00 00                          ........
> [  494.710068] Redzone ffff8804e4730e58: 00 00 00 00 00 00 00 00                          ........
> [  494.710068] Padding ffff8804e4730f98: 00 00 00 00 00 00 00 00                          ........
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