Messages in this thread Patch in this message | | | Date | Tue, 19 Aug 2008 19:43:45 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH 1/1] mm_owner: fix cgroup null dereference |
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* Jiri Slaby <jirislaby@gmail.com> [2008-08-14 22:16:53]:
> Hi, > > found this in mmotm, a fix for > mm-owner-fix-race-between-swap-and-exit.patch >
Does the patch below fix your problem, it's against mmotm 19th August 2008.
Reported-by: jirislaby@gmail.com
Jiri reported a problem and saw an oops when the memrlimit-fix-race-with-swap patch is applied. He sent his patch on top to fix the problem, but ran into another issue. The root cause of the problem is that we are not suppose to call task_cgroup on NULL tasks. This patch reverts Jiri's patch and does not call task_cgroup if the passed task_struct (old) is NULL.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> ---
kernel/cgroup.c | 5 +++-- kernel/exit.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-)
diff -puN kernel/exit.c~memrlimit-fix-race-with-swap-oops kernel/exit.c --- linux-2.6.27-rc3/kernel/exit.c~memrlimit-fix-race-with-swap-oops 2008-08-19 18:50:39.000000000 +0530 +++ linux-2.6.27-rc3-balbir/kernel/exit.c 2008-08-19 18:51:05.000000000 +0530 @@ -641,8 +641,8 @@ retry: * the callback and take action */ down_write(&mm->mmap_sem); - cgroup_mm_owner_callbacks(mm->owner, NULL); mm->owner = NULL; + cgroup_mm_owner_callbacks(mm->owner, NULL); up_write(&mm->mmap_sem); return; diff -puN kernel/cgroup.c~memrlimit-fix-race-with-swap-oops kernel/cgroup.c --- linux-2.6.27-rc3/kernel/cgroup.c~memrlimit-fix-race-with-swap-oops 2008-08-19 18:50:39.000000000 +0530 +++ linux-2.6.27-rc3-balbir/kernel/cgroup.c 2008-08-19 18:55:38.000000000 +0530 @@ -2743,13 +2743,14 @@ void cgroup_fork_callbacks(struct task_s */ void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new) { - struct cgroup *oldcgrp, *newcgrp = NULL; + struct cgroup *oldcgrp = NULL, *newcgrp = NULL; if (need_mm_owner_callback) { int i; for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; - oldcgrp = task_cgroup(old, ss->subsys_id); + if (old) + oldcgrp = task_cgroup(old, ss->subsys_id); if (new) newcgrp = task_cgroup(new, ss->subsys_id); if (oldcgrp == newcgrp) diff -puN mm/memrlimitcgroup.c~memrlimit-fix-race-with-swap-oops mm/memrlimitcgroup.c _ -- Balbir
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