linux-kernel - Re: [PATCH 1/5] uprobes: uprobe_mmap/munmap needs list_for_each_entry

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Message-ID: <20120712055906.GD3598@linux.vnet.ibm.com>
Date:	Thu, 12 Jul 2012 11:29:06 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] uprobes: uprobe_mmap/munmap needs
 list_for_each_entry_safe()

* Oleg Nesterov <oleg@...hat.com> [2012-07-08 22:30:01]:

> The bug was introduced by me in 449d0d7c "uprobes: Simplify the
> usage of uprobe->pending_list".
> 
> Yes, we do not care about uprobe->pending_list after return and
> nobody can remove the current list entry, but put_uprobe(uprobe)
> can actually free it and thus we need list_for_each_safe().
> 
> Reported-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>


Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  kernel/events/uprobes.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 67697db..a93b6df 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1010,7 +1010,7 @@ static void build_probe_list(struct inode *inode, struct list_head *head)
>  int uprobe_mmap(struct vm_area_struct *vma)
>  {
>  	struct list_head tmp_list;
> -	struct uprobe *uprobe;
> +	struct uprobe *uprobe, *u;
>  	struct inode *inode;
>  	int ret, count;
> 
> @@ -1028,7 +1028,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
>  	ret = 0;
>  	count = 0;
> 
> -	list_for_each_entry(uprobe, &tmp_list, pending_list) {
> +	list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
>  		if (!ret) {
>  			loff_t vaddr = vma_address(vma, uprobe->offset);
> 
> @@ -1076,7 +1076,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
>  void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
>  {
>  	struct list_head tmp_list;
> -	struct uprobe *uprobe;
> +	struct uprobe *uprobe, *u;
>  	struct inode *inode;
> 
>  	if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
> @@ -1093,7 +1093,7 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
>  	mutex_lock(uprobes_mmap_hash(inode));
>  	build_probe_list(inode, &tmp_list);
> 
> -	list_for_each_entry(uprobe, &tmp_list, pending_list) {
> +	list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
>  		loff_t vaddr = vma_address(vma, uprobe->offset);
> 
>  		if (vaddr >= start && vaddr < end) {
> -- 
> 1.5.5.1
> 

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