[PATCH] sysfs: Replace %p with %pK in the warning of sysfs_emit*

[PATCH] sysfs: Replace %p with %pK in the warning of sysfs_emit*

[Kyle Tso]

According to Documentation/core-api/printk-formats.rst, kernel pointers
need to be printed with %pK format specifier to respect kptr_restrict in
sysctl.

Also replace the function names in the strings with %s and __func__ as
checkpatch.pl suggested.

Signed-off-by: Kyle Tso <kyletso@google.com>
---
 fs/sysfs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index a12ac0356c69..56712f0886ef 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -732,7 +732,7 @@ int sysfs_emit(char *buf, const char *fmt, ...)
 	int len;
 
 	if (WARN(!buf || offset_in_page(buf),
-		 "invalid sysfs_emit: buf:%p\n", buf))
+		 "invalid %s: buf:%pK\n", __func__, buf))
 		return 0;
 
 	va_start(args, fmt);
@@ -760,7 +760,7 @@ int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
 	int len;
 
 	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
-		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
+		 "invalid %s: buf:%pK at:%d\n", __func__, buf, at))
 		return 0;
 
 	va_start(args, fmt);
-- 
2.41.0.162.gfafddb0af9-goog

Re: [PATCH] sysfs: Replace %p with %pK in the warning of sysfs_emit*

[Greg KH]

On Fri, Jun 23, 2023 at 10:20:54PM +0800, Kyle Tso wrote:
> According to Documentation/core-api/printk-formats.rst, kernel pointers
> need to be printed with %pK format specifier to respect kptr_restrict in
> sysctl.
> 
> Also replace the function names in the strings with %s and __func__ as
> checkpatch.pl suggested.
> 
> Signed-off-by: Kyle Tso <kyletso@google.com>
> ---
>  fs/sysfs/file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> index a12ac0356c69..56712f0886ef 100644
> --- a/fs/sysfs/file.c
> +++ b/fs/sysfs/file.c
> @@ -732,7 +732,7 @@ int sysfs_emit(char *buf, const char *fmt, ...)
>  	int len;
>  
>  	if (WARN(!buf || offset_in_page(buf),
> -		 "invalid sysfs_emit: buf:%p\n", buf))
> +		 "invalid %s: buf:%pK\n", __func__, buf))

Wait, no, these are not going out in sysfs files, as they are still
going to dmesg, right?

So I think this line in the documentation matters:
	This modifier is *only* intended when producing content of a file read by
	userspace from e.g. procfs or sysfs, not for dmesg. Please refer to the
	section about %p above for discussion about how to manage hashing pointers
	in printk().

so %p should still be ok here, the hashed value will end up in the
kernerl log, which is what we want, and the WARN() traceback will show
the problem properly, right?

>  		return 0;
>  
>  	va_start(args, fmt);
> @@ -760,7 +760,7 @@ int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
>  	int len;
>  
>  	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
> -		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
> +		 "invalid %s: buf:%pK at:%d\n", __func__, buf, at))


Same here, %p should be correct.

Sorry for missing this before.

greg k-h

Re: [PATCH] sysfs: Replace %p with %pK in the warning of sysfs_emit*

[Kyle Tso]

On Fri, Jun 23, 2023 at 10:30 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Fri, Jun 23, 2023 at 10:20:54PM +0800, Kyle Tso wrote:
> > According to Documentation/core-api/printk-formats.rst, kernel pointers
> > need to be printed with %pK format specifier to respect kptr_restrict in
> > sysctl.
> >
> > Also replace the function names in the strings with %s and __func__ as
> > checkpatch.pl suggested.
> >
> > Signed-off-by: Kyle Tso <kyletso@google.com>
> > ---
> >  fs/sysfs/file.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
> > index a12ac0356c69..56712f0886ef 100644
> > --- a/fs/sysfs/file.c
> > +++ b/fs/sysfs/file.c
> > @@ -732,7 +732,7 @@ int sysfs_emit(char *buf, const char *fmt, ...)
> >       int len;
> >
> >       if (WARN(!buf || offset_in_page(buf),
> > -              "invalid sysfs_emit: buf:%p\n", buf))
> > +              "invalid %s: buf:%pK\n", __func__, buf))
>
> Wait, no, these are not going out in sysfs files, as they are still
> going to dmesg, right?
>
> So I think this line in the documentation matters:
>         This modifier is *only* intended when producing content of a file read by
>         userspace from e.g. procfs or sysfs, not for dmesg. Please refer to the
>         section about %p above for discussion about how to manage hashing pointers
>         in printk().
>
> so %p should still be ok here, the hashed value will end up in the
> kernerl log, which is what we want, and the WARN() traceback will show
> the problem properly, right?
>
> >               return 0;
> >
> >       va_start(args, fmt);
> > @@ -760,7 +760,7 @@ int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
> >       int len;
> >
> >       if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
> > -              "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
> > +              "invalid %s: buf:%pK at:%d\n", __func__, buf, at))
>
>
> Same here, %p should be correct.
>
> Sorry for missing this before.
>
> greg k-h

Yes, you are right. Sorry for the noise.

Kyle