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* [PATCH] fs: proc: fix error return code of proc_map_files_readdir()
@ 2021-03-09  9:55 Jia-Ju Bai
  2021-03-09 18:30 ` Eric Biggers
  0 siblings, 1 reply; 4+ messages in thread
From: Jia-Ju Bai @ 2021-03-09  9:55 UTC (permalink / raw)
  To: adobriyan, christian, ebiederm, akpm, keescook, gladkov.alexey,
	walken, bernd.edlinger, avagin, deller
  Cc: linux-kernel, linux-fsdevel, Jia-Ju Bai

When get_task_mm() returns NULL to mm, no error return code of
proc_map_files_readdir() is assigned.
To fix this bug, ret is assigned with -ENOENT in this case.

Fixes: f0c3b5093add ("[readdir] convert procfs")
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 fs/proc/base.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3851bfcdba56..254cc6ac65fb 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2332,8 +2332,10 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		goto out_put_task;
 
 	mm = get_task_mm(task);
-	if (!mm)
+	if (!mm) {
+		ret = -ENOENT;
 		goto out_put_task;
+	}
 
 	ret = mmap_read_lock_killable(mm);
 	if (ret) {
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [PATCH] fs: proc: fix error return code of proc_map_files_readdir()
  2021-03-09  9:55 [PATCH] fs: proc: fix error return code of proc_map_files_readdir() Jia-Ju Bai
@ 2021-03-09 18:30 ` Eric Biggers
  2021-03-09 19:05   ` Alexey Dobriyan
  0 siblings, 1 reply; 4+ messages in thread
From: Eric Biggers @ 2021-03-09 18:30 UTC (permalink / raw)
  To: Jia-Ju Bai
  Cc: adobriyan, christian, ebiederm, akpm, keescook, gladkov.alexey,
	walken, bernd.edlinger, avagin, deller, linux-kernel,
	linux-fsdevel

On Tue, Mar 09, 2021 at 01:55:27AM -0800, Jia-Ju Bai wrote:
> When get_task_mm() returns NULL to mm, no error return code of
> proc_map_files_readdir() is assigned.
> To fix this bug, ret is assigned with -ENOENT in this case.
> 
> Fixes: f0c3b5093add ("[readdir] convert procfs")
> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
>  fs/proc/base.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 3851bfcdba56..254cc6ac65fb 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2332,8 +2332,10 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
>  		goto out_put_task;
>  
>  	mm = get_task_mm(task);
> -	if (!mm)
> +	if (!mm) {
> +		ret = -ENOENT;
>  		goto out_put_task;
> +	}
>  
>  	ret = mmap_read_lock_killable(mm);

Is there something in particular that makes you think that returning ENOENT is
the correct behavior in this case?  Try 'ls /proc/$pid/map_files' where pid is a
kernel thread; it's an empty directory, which is probably intentional.  Your
patch would change reading the directory to fail with ENOENT.

- Eric

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] fs: proc: fix error return code of proc_map_files_readdir()
  2021-03-09 18:30 ` Eric Biggers
@ 2021-03-09 19:05   ` Alexey Dobriyan
  2021-03-10  1:11     ` Jia-Ju Bai
  0 siblings, 1 reply; 4+ messages in thread
From: Alexey Dobriyan @ 2021-03-09 19:05 UTC (permalink / raw)
  To: Eric Biggers
  Cc: Jia-Ju Bai, christian, ebiederm, akpm, keescook, gladkov.alexey,
	walken, bernd.edlinger, avagin, deller, linux-kernel,
	linux-fsdevel

On Tue, Mar 09, 2021 at 10:30:23AM -0800, Eric Biggers wrote:
> On Tue, Mar 09, 2021 at 01:55:27AM -0800, Jia-Ju Bai wrote:
> > When get_task_mm() returns NULL to mm, no error return code of
> > proc_map_files_readdir() is assigned.
> > To fix this bug, ret is assigned with -ENOENT in this case.

> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -2332,8 +2332,10 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
> >  		goto out_put_task;
> >  
> >  	mm = get_task_mm(task);
> > -	if (!mm)
> > +	if (!mm) {
> > +		ret = -ENOENT;
> >  		goto out_put_task;
> > +	}
> >  
> >  	ret = mmap_read_lock_killable(mm);
> 
> Is there something in particular that makes you think that returning ENOENT is
> the correct behavior in this case?  Try 'ls /proc/$pid/map_files' where pid is a
> kernel thread; it's an empty directory, which is probably intentional.  Your
> patch would change reading the directory to fail with ENOENT.

Yes. 0 from readdir means "no more stuff", not an error.

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] fs: proc: fix error return code of proc_map_files_readdir()
  2021-03-09 19:05   ` Alexey Dobriyan
@ 2021-03-10  1:11     ` Jia-Ju Bai
  0 siblings, 0 replies; 4+ messages in thread
From: Jia-Ju Bai @ 2021-03-10  1:11 UTC (permalink / raw)
  To: Alexey Dobriyan, Eric Biggers
  Cc: christian, ebiederm, akpm, keescook, gladkov.alexey, walken,
	bernd.edlinger, avagin, deller, linux-kernel, linux-fsdevel



On 2021/3/10 3:05, Alexey Dobriyan wrote:
> On Tue, Mar 09, 2021 at 10:30:23AM -0800, Eric Biggers wrote:
>
>>> --- a/fs/proc/base.c
>>> +++ b/fs/proc/base.c
>>> @@ -2332,8 +2332,10 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
>>>   		goto out_put_task;
>>>   
>>>   	mm = get_task_mm(task);
>>> -	if (!mm)
>>> +	if (!mm) {
>>> +		ret = -ENOENT;
>>>   		goto out_put_task;
>>> +	}
>>>   
>>>   	ret = mmap_read_lock_killable(mm);
>> Is there something in particular that makes you think that returning ENOENT is
>> the correct behavior in this case?  Try 'ls /proc/$pid/map_files' where pid is a
>> kernel thread; it's an empty directory, which is probably intentional.  Your
>> patch would change reading the directory to fail with ENOENT.
> Yes. 0 from readdir means "no more stuff", not an error.

Thanks for your reply and explanation.
I am sorry for the false report...


Best wishes,
Jia-Ju Bai

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-03-10  1:12 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-03-09  9:55 [PATCH] fs: proc: fix error return code of proc_map_files_readdir() Jia-Ju Bai
2021-03-09 18:30 ` Eric Biggers
2021-03-09 19:05   ` Alexey Dobriyan
2021-03-10  1:11     ` Jia-Ju Bai

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