[PATCH] fs/proc/task_mmu.c: fix clear_refs_write() input sanity check

[PATCH] fs/proc/task_mmu.c: fix clear_refs_write() input sanity check

[Vincent Li]

Andrew Morton pointed out similar string hacking and obfuscated check for zero-length input
at the end of the function, David Rientjes suggested to use strict_strtol to replace
simple_strtol, this patch cover above suggestions, add removing of leading and trailing
whitespace from user input. It does not change function behavious. 

This patch is rebased on mmotm-2009-08-04-14-22.

Signed-off-by: Vincent Li <macli@brc.ubc.ca>
---
 fs/proc/task_mmu.c |   18 ++++++++----------
 1 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2079969..026b532 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -494,18 +494,17 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 	char buffer[PROC_NUMBUF], *end;
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
-	int type;
+	long res;
 
 	memset(buffer, 0, sizeof(buffer));
 	if (count > sizeof(buffer) - 1)
 		count = sizeof(buffer) - 1;
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
-	type = simple_strtol(buffer, &end, 0);
-	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
+	if (strict_strtol(strstrip(buffer), 10, &res)
+		return -EINVAL;
+	if (res < CLEAR_REFS_ALL || res > CLEAR_REFS_MAPPED)
 		return -EINVAL;
-	if (*end == '\n')
-		end++;
 	task = get_proc_task(file->f_path.dentry->d_inode);
 	if (!task)
 		return -ESRCH;
@@ -529,9 +528,9 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 			 * Writing 3 to /proc/pid/clear_refs only affects file
 			 * mapped pages.
 			 */
-			if (type == CLEAR_REFS_ANON && vma->vm_file)
+			if (res == CLEAR_REFS_ANON && vma->vm_file)
 				continue;
-			if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
+			if (res == CLEAR_REFS_MAPPED && !vma->vm_file)
 				continue;
 			walk_page_range(vma->vm_start, vma->vm_end,
 					&clear_refs_walk);
@@ -541,9 +540,8 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 		mmput(mm);
 	}
 	put_task_struct(task);
-	if (end - buffer == 0)
-		return -EIO;
-	return end - buffer;
+
+	return count;
 }
 
 const struct file_operations proc_clear_refs_operations = {
-- 
1.6.0.4

Re: [PATCH] fs/proc/task_mmu.c: fix clear_refs_write() input sanity check

[David Rientjes]

On Wed, 12 Aug 2009, Vincent Li wrote:

> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 2079969..026b532 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -494,18 +494,17 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
>  	char buffer[PROC_NUMBUF], *end;
>  	struct mm_struct *mm;
>  	struct vm_area_struct *vma;
> -	int type;
> +	long res;
>  

What does `res' mean?  Why can't it just be left as `type'?

>  	memset(buffer, 0, sizeof(buffer));
>  	if (count > sizeof(buffer) - 1)
>  		count = sizeof(buffer) - 1;
>  	if (copy_from_user(buffer, buf, count))
>  		return -EFAULT;
> -	type = simple_strtol(buffer, &end, 0);
> -	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
> +	if (strict_strtol(strstrip(buffer), 10, &res)
> +		return -EINVAL;

Please test your patch submissions (which would require that the above 
actually compiles).

Re: [PATCH] fs/proc/task_mmu.c: fix clear_refs_write() input sanity check

[Li, Ming Chun]

On Wed, 12 Aug 2009, David Rientjes wrote:

> On Wed, 12 Aug 2009, Vincent Li wrote:
> 
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 2079969..026b532 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -494,18 +494,17 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
> >  	char buffer[PROC_NUMBUF], *end;
> >  	struct mm_struct *mm;
> >  	struct vm_area_struct *vma;
> > -	int type;
> > +	long res;
> >  
> 
> What does `res' mean?  Why can't it just be left as `type'?

res mean the result parsed from userspace input, I can keep it as name 
'type'.

> 
> >  	memset(buffer, 0, sizeof(buffer));
> >  	if (count > sizeof(buffer) - 1)
> >  		count = sizeof(buffer) - 1;
> >  	if (copy_from_user(buffer, buf, count))
> >  		return -EFAULT;
> > -	type = simple_strtol(buffer, &end, 0);
> > -	if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
> > +	if (strict_strtol(strstrip(buffer), 10, &res)
> > +		return -EINVAL;
> 
> Please test your patch submissions (which would require that the above 
> actually compiles).
> 

I did get compiling error and warnings, I will resend the patch with 
varible name 'type' left and no compiling errors.


Vincent Li
Biomedical Research Center
University of British Columbia