Re: [PATCH] sysfs: turn WARN() into pr_warn()

[Dmitry Vyukov]

On Mon, Jan 22, 2018 at 3:57 PM, Greg KH  wrote:
> From: Greg Kroah-Hartman 
>
> It's not good to crash the machine if panic_on_warn() is set just
> because someone made a stupid mistake of trying to create a sysfs file
> with the same name of an existing one.  This makes the automated testing
> tools a lot harder to find the real bugs in the kernel.
>
> So just print a warning out and dump the stack to get the attention of
> the developer that they did something foolish.  Then keep on trucking,
> as this should not be a fatal error at all.
>
> Reported-by: Dmitry Vyukov 
> Signed-off-by: Greg Kroah-Hartman 
> ---
>
> Dmitry, does this look good to you?  If so, I'll queue it up for
> 4.16-rc1.

Perfect! Looks good. syzbot reacts on "WARNING:" string (+ if kernel
panic due to panic_on_warn that's also obviously a problem).

> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index 2b67bda2021b..3a36a48a4b3f 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -10,6 +10,7 @@
>   * Please see Documentation/filesystems/sysfs.txt for more information.
>   */
>
> +#define pr_fmt(fmt)"sysfs: " fmt
>  #undef DEBUG
>
>  #include 
> @@ -27,8 +28,8 @@ void sysfs_warn_dup(struct kernfs_node *parent, const char 
> *name)
> if (buf)
> kernfs_path(parent, buf, PATH_MAX);
>
> -   WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename 
> '%s/%s'\n",
> -buf, name);
> +   pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
> +   dump_stack();
>
> kfree(buf);
>  }

[PATCH] sysfs: turn WARN() into pr_warn()

[Greg KH]

From: Greg Kroah-Hartman 

It's not good to crash the machine if panic_on_warn() is set just
because someone made a stupid mistake of trying to create a sysfs file
with the same name of an existing one.  This makes the automated testing
tools a lot harder to find the real bugs in the kernel.

So just print a warning out and dump the stack to get the attention of
the developer that they did something foolish.  Then keep on trucking,
as this should not be a fatal error at all.

Reported-by: Dmitry Vyukov 
Signed-off-by: Greg Kroah-Hartman 
---

Dmitry, does this look good to you?  If so, I'll queue it up for
4.16-rc1.


diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 2b67bda2021b..3a36a48a4b3f 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -10,6 +10,7 @@
  * Please see Documentation/filesystems/sysfs.txt for more information.
  */
 
+#define pr_fmt(fmt)"sysfs: " fmt
 #undef DEBUG
 
 #include 
@@ -27,8 +28,8 @@ void sysfs_warn_dup(struct kernfs_node *parent, const char 
*name)
if (buf)
kernfs_path(parent, buf, PATH_MAX);
 
-   WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename 
'%s/%s'\n",
-buf, name);
+   pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
+   dump_stack();
 
kfree(buf);
 }