Re: [PATCH V2] perf cpumap: Fix snprintf overflow check

[Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>]

Le 24/03/2020 à 13:50, Arnaldo Carvalho de Melo a écrit :
> Em Tue, Mar 24, 2020 at 08:03:19AM +0100, Christophe JAILLET escreveu:
> > 'snprintf' returns the number of characters which would be generated for
> > the given input.
> >
> > If the returned value is *greater than* or equal to the buffer size, it
> > means that the output has been truncated.
> >
> > Fix the overflow test accordingling.
>                                    y
>
> You forgot to CC David and add this to your patch, which I did:
>
> Suggested-by: David Laight <David.Laight@xxxxxxxxxx>
>
> Ok?

No problem for me.

The to: and cc: list are (at least should be :)) the ones given by 
get_maintainer, and I was not aware of the 'Suggested-by' tag.

BTW, thanks for fixing the typo in the description.

CJ


> - Arnaldo
>   
> > Fixes: 7780c25bae59f ("perf tools: Allow ability to map cpus to nodes easily")
> > Fixes: 92a7e1278005b ("perf cpumap: Add cpu__max_present_cpu()")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> > V2: keep snprintf
> >      modifiy the tests for truncated output
> >      Update subject and description
> > ---
> >   tools/perf/util/cpumap.c | 10 +++++-----
> >   1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> > index 983b7388f22b..dc5c5e6fc502 100644
> > --- a/tools/perf/util/cpumap.c
> > +++ b/tools/perf/util/cpumap.c
> > @@ -317,7 +317,7 @@ static void set_max_cpu_num(void)
> >   
> >   	/* get the highest possible cpu number for a sparse allocation */
> >   	ret = snprintf(path, PATH_MAX, "%s/devices/system/cpu/possible", mnt);
> > -	if (ret == PATH_MAX) {
> > +	if (ret >= PATH_MAX) {
> >   		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
> >   		goto out;
> >   	}
> > @@ -328,7 +328,7 @@ static void set_max_cpu_num(void)
> >   
> >   	/* get the highest present cpu number for a sparse allocation */
> >   	ret = snprintf(path, PATH_MAX, "%s/devices/system/cpu/present", mnt);
> > -	if (ret == PATH_MAX) {
> > +	if (ret >= PATH_MAX) {
> >   		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
> >   		goto out;
> >   	}
> > @@ -356,7 +356,7 @@ static void set_max_node_num(void)
> >   
> >   	/* get the highest possible cpu number for a sparse allocation */
> >   	ret = snprintf(path, PATH_MAX, "%s/devices/system/node/possible", mnt);
> > -	if (ret == PATH_MAX) {
> > +	if (ret >= PATH_MAX) {
> >   		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
> >   		goto out;
> >   	}
> > @@ -441,7 +441,7 @@ int cpu__setup_cpunode_map(void)
> >   		return 0;
> >   
> >   	n = snprintf(path, PATH_MAX, "%s/devices/system/node", mnt);
> > -	if (n == PATH_MAX) {
> > +	if (n >= PATH_MAX) {
> >   		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
> >   		return -1;
> >   	}
> > @@ -456,7 +456,7 @@ int cpu__setup_cpunode_map(void)
> >   			continue;
> >   
> >   		n = snprintf(buf, PATH_MAX, "%s/%s", path, dent1->d_name);
> > -		if (n == PATH_MAX) {
> > +		if (n >= PATH_MAX) {
> >   			pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
> >   			continue;
> >   		}
> > --
> > 2.20.1