[char-misc] mei: trace: treat reg parameter as string

[char-misc] mei: trace: treat reg parameter as string

[Alexander Usyskin]

Process the reg string parameter in secure way.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
---
 drivers/misc/mei/mei-trace.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/mei/mei-trace.h b/drivers/misc/mei/mei-trace.h
index 5312edbf5190..24fa321d88bd 100644
--- a/drivers/misc/mei/mei-trace.h
+++ b/drivers/misc/mei/mei-trace.h
@@ -21,18 +21,18 @@ TRACE_EVENT(mei_reg_read,
 	TP_ARGS(dev, reg, offs, val),
 	TP_STRUCT__entry(
 		__string(dev, dev_name(dev))
-		__field(const char *, reg)
+		__string(reg, reg)
 		__field(u32, offs)
 		__field(u32, val)
 	),
 	TP_fast_assign(
 		__assign_str(dev);
-		__entry->reg  = reg;
+		__assign_str(reg);
 		__entry->offs = offs;
 		__entry->val = val;
 	),
 	TP_printk("[%s] read %s:[%#x] = %#x",
-		  __get_str(dev), __entry->reg, __entry->offs, __entry->val)
+		  __get_str(dev), __get_str(reg), __entry->offs, __entry->val)
 );
 
 TRACE_EVENT(mei_reg_write,
@@ -40,18 +40,18 @@ TRACE_EVENT(mei_reg_write,
 	TP_ARGS(dev, reg, offs, val),
 	TP_STRUCT__entry(
 		__string(dev, dev_name(dev))
-		__field(const char *, reg)
+		__string(reg, reg)
 		__field(u32, offs)
 		__field(u32, val)
 	),
 	TP_fast_assign(
 		__assign_str(dev);
-		__entry->reg = reg;
+		__assign_str(reg);
 		__entry->offs = offs;
 		__entry->val = val;
 	),
 	TP_printk("[%s] write %s[%#x] = %#x",
-		  __get_str(dev), __entry->reg,  __entry->offs, __entry->val)
+		  __get_str(dev), __get_str(reg),  __entry->offs, __entry->val)
 );
 
 TRACE_EVENT(mei_pci_cfg_read,
@@ -59,18 +59,18 @@ TRACE_EVENT(mei_pci_cfg_read,
 	TP_ARGS(dev, reg, offs, val),
 	TP_STRUCT__entry(
 		__string(dev, dev_name(dev))
-		__field(const char *, reg)
+		__string(reg, reg)
 		__field(u32, offs)
 		__field(u32, val)
 	),
 	TP_fast_assign(
 		__assign_str(dev);
-		__entry->reg  = reg;
+		__assign_str(reg);
 		__entry->offs = offs;
 		__entry->val = val;
 	),
 	TP_printk("[%s] pci cfg read %s:[%#x] = %#x",
-		  __get_str(dev), __entry->reg, __entry->offs, __entry->val)
+		  __get_str(dev), __get_str(reg), __entry->offs, __entry->val)
 );
 
 #endif /* _MEI_TRACE_H_ */
-- 
2.43.0

Re: [char-misc] mei: trace: treat reg parameter as string

[Greg Kroah-Hartman]

On Sun, Jan 04, 2026 at 10:20:44AM +0200, Alexander Usyskin wrote:
> Process the reg string parameter in secure way.
> 

I'm sorry, but I don't understand this changelog text.  What exactly is
this doing?  Why is a string "better" than a char *?

thanks,

greg k-h

RE: [char-misc] mei: trace: treat reg parameter as string

[Usyskin, Alexander]

> Subject: Re: [char-misc] mei: trace: treat reg parameter as string
> 
> On Sun, Jan 04, 2026 at 10:20:44AM +0200, Alexander Usyskin wrote:
> > Process the reg string parameter in secure way.
> >
> 
> I'm sorry, but I don't understand this changelog text.  What exactly is
> this doing?  Why is a string "better" than a char *?
> 
> thanks,
> 
> greg k-h

Sorry, I'm bad in changelogs, trying to improve...

The string wrapper checks sanity of parameters and prevents internal kernel data leaks.
Newer kernels refuse to emit event with plain char*, without the wrapper.
See https://elixir.bootlin.com/linux/v6.19-rc3/source/kernel/trace/trace.c#L3785

- - 
Thanks,
Sasha

Re: [char-misc] mei: trace: treat reg parameter as string

[Greg Kroah-Hartman]

On Tue, Jan 06, 2026 at 10:59:26AM +0000, Usyskin, Alexander wrote:
> > Subject: Re: [char-misc] mei: trace: treat reg parameter as string
> > 
> > On Sun, Jan 04, 2026 at 10:20:44AM +0200, Alexander Usyskin wrote:
> > > Process the reg string parameter in secure way.
> > >
> > 
> > I'm sorry, but I don't understand this changelog text.  What exactly is
> > this doing?  Why is a string "better" than a char *?
> > 
> > thanks,
> > 
> > greg k-h
> 
> Sorry, I'm bad in changelogs, trying to improve...

It is usually the hardest part of making a code change.

> The string wrapper checks sanity of parameters and prevents internal kernel data leaks.
> Newer kernels refuse to emit event with plain char*, without the wrapper.
> See https://elixir.bootlin.com/linux/v6.19-rc3/source/kernel/trace/trace.c#L3785

Great, please take this information and rewrite this to explain the need
here and what this change is doing.

thanks,

greg k-h