Patchwork [net,v3,1/3] net: netprio: fix files lock and remove useless d_path bits

login
register
mail settings
Submitter John Fastabend
Date Aug. 14, 2012, 10:34 p.m.
Message ID <20120814223424.3551.21608.stgit@jf-dev1-dcblab>
Download mbox | patch
Permalink /patch/177470/
State Accepted
Delegated to: David Miller
Headers show

Comments

John Fastabend - Aug. 14, 2012, 10:34 p.m.
Add lock to prevent a race with a file closing and also remove
useless and ugly sscanf code. The extra code was never needed
and the case it supposedly protected against is in fact handled
correctly by sock_from_file as pointed out by Al Viro.

CC: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
---

 net/core/netprio_cgroup.c |   22 ++++------------------
 1 files changed, 4 insertions(+), 18 deletions(-)


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Neil Horman - Aug. 15, 2012, 10:52 a.m.
On Tue, Aug 14, 2012 at 03:34:24PM -0700, John Fastabend wrote:
> Add lock to prevent a race with a file closing and also remove
> useless and ugly sscanf code. The extra code was never needed
> and the case it supposedly protected against is in fact handled
> correctly by sock_from_file as pointed out by Al Viro.
> 
> CC: Neil Horman <nhorman@tuxdriver.com>
> Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> ---
> 
>  net/core/netprio_cgroup.c |   22 ++++------------------
>  1 files changed, 4 insertions(+), 18 deletions(-)
> 
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index ed0c043..f65dba3 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -277,12 +277,6 @@ out_free_devname:
>  void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
>  {
>  	struct task_struct *p;
> -	char *tmp = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
> -
> -	if (!tmp) {
> -		pr_warn("Unable to attach cgrp due to alloc failure!\n");
> -		return;
> -	}
>  
>  	cgroup_taskset_for_each(p, cgrp, tset) {
>  		unsigned int fd;
> @@ -296,32 +290,24 @@ void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
>  			continue;
>  		}
>  
> -		rcu_read_lock();
> +		spin_lock(&files->file_lock);
>  		fdt = files_fdtable(files);
>  		for (fd = 0; fd < fdt->max_fds; fd++) {
> -			char *path;
>  			struct file *file;
>  			struct socket *sock;
> -			unsigned long s;
> -			int rv, err = 0;
> +			int err;
>  
>  			file = fcheck_files(files, fd);
>  			if (!file)
>  				continue;
>  
> -			path = d_path(&file->f_path, tmp, PAGE_SIZE);
> -			rv = sscanf(path, "socket:[%lu]", &s);
> -			if (rv <= 0)
> -				continue;
> -
>  			sock = sock_from_file(file, &err);
> -			if (!err)
> +			if (sock)
>  				sock_update_netprioidx(sock->sk, p);
>  		}
> -		rcu_read_unlock();
> +		spin_unlock(&files->file_lock);
>  		task_unlock(p);
>  	}
> -	kfree(tmp);
>  }
>  
>  static struct cftype ss_files[] = {
> 
> 
Acked-by: Neil Horman <nhorman@tuxdriver.com>

It looks good to me.  Al, could you please lend your review here too?
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Al Viro - Aug. 15, 2012, 8:03 p.m.
On Wed, Aug 15, 2012 at 06:52:06AM -0400, Neil Horman wrote:
> On Tue, Aug 14, 2012 at 03:34:24PM -0700, John Fastabend wrote:
> > Add lock to prevent a race with a file closing and also remove
> > useless and ugly sscanf code. The extra code was never needed
> > and the case it supposedly protected against is in fact handled
> > correctly by sock_from_file as pointed out by Al Viro.
> > 
> > CC: Neil Horman <nhorman@tuxdriver.com>
> > Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> > Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> > ---
> > 
> >  net/core/netprio_cgroup.c |   22 ++++------------------
> >  1 files changed, 4 insertions(+), 18 deletions(-)
> > 
> > diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> > index ed0c043..f65dba3 100644
> > --- a/net/core/netprio_cgroup.c
> > +++ b/net/core/netprio_cgroup.c
> > @@ -277,12 +277,6 @@ out_free_devname:
> >  void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
> >  {
> >  	struct task_struct *p;
> > -	char *tmp = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
> > -
> > -	if (!tmp) {
> > -		pr_warn("Unable to attach cgrp due to alloc failure!\n");
> > -		return;
> > -	}
> >  
> >  	cgroup_taskset_for_each(p, cgrp, tset) {
> >  		unsigned int fd;
> > @@ -296,32 +290,24 @@ void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
> >  			continue;
> >  		}
> >  
> > -		rcu_read_lock();
> > +		spin_lock(&files->file_lock);
> >  		fdt = files_fdtable(files);
> >  		for (fd = 0; fd < fdt->max_fds; fd++) {
> > -			char *path;
> >  			struct file *file;
> >  			struct socket *sock;
> > -			unsigned long s;
> > -			int rv, err = 0;
> > +			int err;
> >  
> >  			file = fcheck_files(files, fd);
> >  			if (!file)
> >  				continue;
> >  
> > -			path = d_path(&file->f_path, tmp, PAGE_SIZE);
> > -			rv = sscanf(path, "socket:[%lu]", &s);
> > -			if (rv <= 0)
> > -				continue;
> > -
> >  			sock = sock_from_file(file, &err);
> > -			if (!err)
> > +			if (sock)
> >  				sock_update_netprioidx(sock->sk, p);
> >  		}
> > -		rcu_read_unlock();
> > +		spin_unlock(&files->file_lock);
> >  		task_unlock(p);
> >  	}
> > -	kfree(tmp);
> >  }
> >  
> >  static struct cftype ss_files[] = {
> > 
> > 
> Acked-by: Neil Horman <nhorman@tuxdriver.com>
> 
> It looks good to me.  Al, could you please lend your review here too?

Tolerable...  I still don't like the idea of iterating through the
descriptor tables, but at least that variant is safe wrt locking and
lifetime rules.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
David Miller - Aug. 16, 2012, 10:11 p.m.
From: John Fastabend <john.r.fastabend@intel.com>
Date: Tue, 14 Aug 2012 15:34:24 -0700

> Add lock to prevent a race with a file closing and also remove
> useless and ugly sscanf code. The extra code was never needed
> and the case it supposedly protected against is in fact handled
> correctly by sock_from_file as pointed out by Al Viro.
> 
> CC: Neil Horman <nhorman@tuxdriver.com>
> Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>

Applied.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index ed0c043..f65dba3 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -277,12 +277,6 @@  out_free_devname:
 void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 {
 	struct task_struct *p;
-	char *tmp = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
-
-	if (!tmp) {
-		pr_warn("Unable to attach cgrp due to alloc failure!\n");
-		return;
-	}
 
 	cgroup_taskset_for_each(p, cgrp, tset) {
 		unsigned int fd;
@@ -296,32 +290,24 @@  void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 			continue;
 		}
 
-		rcu_read_lock();
+		spin_lock(&files->file_lock);
 		fdt = files_fdtable(files);
 		for (fd = 0; fd < fdt->max_fds; fd++) {
-			char *path;
 			struct file *file;
 			struct socket *sock;
-			unsigned long s;
-			int rv, err = 0;
+			int err;
 
 			file = fcheck_files(files, fd);
 			if (!file)
 				continue;
 
-			path = d_path(&file->f_path, tmp, PAGE_SIZE);
-			rv = sscanf(path, "socket:[%lu]", &s);
-			if (rv <= 0)
-				continue;
-
 			sock = sock_from_file(file, &err);
-			if (!err)
+			if (sock)
 				sock_update_netprioidx(sock->sk, p);
 		}
-		rcu_read_unlock();
+		spin_unlock(&files->file_lock);
 		task_unlock(p);
 	}
-	kfree(tmp);
 }
 
 static struct cftype ss_files[] = {