From: Jiri Slaby mm->owner is set to NULL prior to calling cgroup_mm_owner_callbacks, but it should be set after that to not pass NULL pointer as the old owner which otherwise results in an oops (shortened): BUG: unable to handle kernel NULL pointer dereference at 0000000000000580 Oops: 0000 [1] SMP Pid: 3396, comm: nscd Tainted: G W 2.6.27-rc3-mm1_64 #439 RIP: 0010:[] [] cgroup_mm_owner_callbacks+0x3a/0x90 RAX: 0000000000000000 RBX: ffffffff80589720 RCX: ffff880079f503e8 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff806c36e0 RBP: ffff880078291bd8 R08: ffff880078290000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: ffff8800787f8e20 Call Trace: [] mm_update_next_owner+0x1ca/0x240 [] exit_mm+0x10a/0x150 [] do_exit+0x1dc/0x940 Code: 89 fe 41 55 49 89 f5 41 54 53 74 68 48 c7 c3 20 97 58 80 45 31 e4 0f 1f 00 48 8b 3b 4d 85 ed 48 63 47 58 48 8d 14 c5 00 00 00 00 <49> 8b 86 80 05 00 00 48 8d 44 10 38 48 8b 00 48 8b 30 74 12 49 Signed-off-by: Jiri Slaby Cc: Balbir Singh Cc: Hugh Dickins Signed-off-by: Andrew Morton --- kernel/exit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN kernel/exit.c~mm-owner-fix-race-between-swap-and-exit-fix kernel/exit.c --- a/kernel/exit.c~mm-owner-fix-race-between-swap-and-exit-fix +++ a/kernel/exit.c @@ -641,8 +641,8 @@ retry: * the callback and take action */ down_write(&mm->mmap_sem); - mm->owner = NULL; cgroup_mm_owner_callbacks(mm->owner, NULL); + mm->owner = NULL; up_write(&mm->mmap_sem); return; _