The commit 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end
and env_start|end in mm_struct") introduce the spinlock arg_lock to protect
the arg_* and env_* field of the mm_struct structure.
While reading the code, I found that this new spinlock was not used in
get_cmdline() to protect access to these fields.
Fixing this even if there is no issue reported yet for this.
Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct")
Cc: Yang Shi <[email protected]>
Signed-off-by: Laurent Dufour <[email protected]>
---
mm/util.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/util.c b/mm/util.c
index 05a464929b3e..789760c3028b 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
if (!mm->arg_end)
goto out_mm; /* Shh! No looking before we're done */
- down_read(&mm->mmap_sem);
+ spin_lock(&mm->arg_lock);
arg_start = mm->arg_start;
arg_end = mm->arg_end;
env_start = mm->env_start;
env_end = mm->env_end;
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->arg_lock);
len = arg_end - arg_start;
--
2.21.0
Michal has posted the same patch few days ago http://lkml.kernel.org/r/[email protected]
On Thu 18-04-19 14:58:27, Laurent Dufour wrote:
> The commit 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end
> and env_start|end in mm_struct") introduce the spinlock arg_lock to protect
> the arg_* and env_* field of the mm_struct structure.
>
> While reading the code, I found that this new spinlock was not used in
> get_cmdline() to protect access to these fields.
>
> Fixing this even if there is no issue reported yet for this.
>
> Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct")
> Cc: Yang Shi <[email protected]>
> Signed-off-by: Laurent Dufour <[email protected]>
> ---
> mm/util.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 05a464929b3e..789760c3028b 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
> if (!mm->arg_end)
> goto out_mm; /* Shh! No looking before we're done */
>
> - down_read(&mm->mmap_sem);
> + spin_lock(&mm->arg_lock);
> arg_start = mm->arg_start;
> arg_end = mm->arg_end;
> env_start = mm->env_start;
> env_end = mm->env_end;
> - up_read(&mm->mmap_sem);
> + spin_unlock(&mm->arg_lock);
>
> len = arg_end - arg_start;
>
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
Le 18/04/2019 à 15:03, Michal Hocko a écrit :
> Michal has posted the same patch few days ago http://lkml.kernel.org/r/[email protected]
Oups, sorry for the noise, I missed it.
> On Thu 18-04-19 14:58:27, Laurent Dufour wrote:
>> The commit 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end
>> and env_start|end in mm_struct") introduce the spinlock arg_lock to protect
>> the arg_* and env_* field of the mm_struct structure.
>>
>> While reading the code, I found that this new spinlock was not used in
>> get_cmdline() to protect access to these fields.
>>
>> Fixing this even if there is no issue reported yet for this.
>>
>> Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct")
>> Cc: Yang Shi <[email protected]>
>> Signed-off-by: Laurent Dufour <[email protected]>
>> ---
>> mm/util.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/util.c b/mm/util.c
>> index 05a464929b3e..789760c3028b 100644
>> --- a/mm/util.c
>> +++ b/mm/util.c
>> @@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
>> if (!mm->arg_end)
>> goto out_mm; /* Shh! No looking before we're done */
>>
>> - down_read(&mm->mmap_sem);
>> + spin_lock(&mm->arg_lock);
>> arg_start = mm->arg_start;
>> arg_end = mm->arg_end;
>> env_start = mm->env_start;
>> env_end = mm->env_end;
>> - up_read(&mm->mmap_sem);
>> + spin_unlock(&mm->arg_lock);
>>
>> len = arg_end - arg_start;
>>
>> --
>> 2.21.0
>
On 4/18/19 6:05 AM, Laurent Dufour wrote:
> Le 18/04/2019 à 15:03, Michal Hocko a écrit :
>> Michal has posted the same patch few days ago
>> http://lkml.kernel.org/r/[email protected]
>
> Oups, sorry for the noise, I missed it.
Yes, Michal already posted a similar patch. Anyway, thanks for catching
this.
>
>> On Thu 18-04-19 14:58:27, Laurent Dufour wrote:
>>> The commit 88aa7cc688d4 ("mm: introduce arg_lock to protect
>>> arg_start|end
>>> and env_start|end in mm_struct") introduce the spinlock arg_lock to
>>> protect
>>> the arg_* and env_* field of the mm_struct structure.
>>>
>>> While reading the code, I found that this new spinlock was not used in
>>> get_cmdline() to protect access to these fields.
>>>
>>> Fixing this even if there is no issue reported yet for this.
>>>
>>> Fixes: 88aa7cc688d4 ("mm: introduce arg_lock to protect
>>> arg_start|end and env_start|end in mm_struct")
>>> Cc: Yang Shi <[email protected]>
>>> Signed-off-by: Laurent Dufour <[email protected]>
>>> ---
>>> mm/util.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/util.c b/mm/util.c
>>> index 05a464929b3e..789760c3028b 100644
>>> --- a/mm/util.c
>>> +++ b/mm/util.c
>>> @@ -758,12 +758,12 @@ int get_cmdline(struct task_struct *task, char
>>> *buffer, int buflen)
>>> if (!mm->arg_end)
>>> goto out_mm; /* Shh! No looking before we're done */
>>> - down_read(&mm->mmap_sem);
>>> + spin_lock(&mm->arg_lock);
>>> arg_start = mm->arg_start;
>>> arg_end = mm->arg_end;
>>> env_start = mm->env_start;
>>> env_end = mm->env_end;
>>> - up_read(&mm->mmap_sem);
>>> + spin_unlock(&mm->arg_lock);
>>> len = arg_end - arg_start;
>>> --
>>> 2.21.0
>>