On Wed, Feb 21, 2024 at 2:05 PM Justin Stitt <[email protected]> wrote: > > I am going to quote Lee Jones who has been doing some snprintf -> > scnprintf refactorings: > > "There is a general misunderstanding amongst engineers that > {v}snprintf() returns the length of the data *actually* encoded into the > destination array. However, as per the C99 standard {v}snprintf() > really returns the length of the data that *would have been* written if > there were enough space for it. This misunderstanding has led to > buffer-overruns in the past. It's generally considered safer to use the > {v}scnprintf() variants in their place (or even sprintf() in simple > cases). So let's do that." > > To help prevent new instances of snprintf() from popping up, let's add a > check to checkpatch.pl. > > Suggested-by: Finn Thain <[email protected]> > Signed-off-by: Justin Stitt <[email protected]> > --- > From a discussion here [1]. > > [1]: > https://lore.kernel.org/all/[email protected]/ > --- > scripts/checkpatch.pl | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 9c4c4a61bc83..bb4e99c818a9 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -7012,6 +7012,12 @@ sub process { > "Prefer strscpy, strscpy_pad, or __nonstring > over strncpy - see: https://github.com/KSPP/linux/issues/90\n"; . $herecurr); > } > > +# snprintf uses that should likely be {v}scnprintf > + if ($line =~ /\snprintf\s*\(\s*/) { > + WARN("SNPRINTF", > + "Prefer scnprintf over snprintf\n" . > $herecurr);
Whoops, I dropped the \b with some poor vim skills. v2 is up. [v2]: https://lore.kernel.org/r/[email protected] > + } > + > # ethtool_sprintf uses that should likely be ethtool_puts > if ($line =~ > /\bethtool_sprintf\s*\(\s*$FuncArg\s*,\s*$FuncArg\s*\)/) { > if (WARN("PREFER_ETHTOOL_PUTS", > > --- > base-commit: b401b621758e46812da61fa58a67c3fd8d91de0d > change-id: 20240221-snprintf-checkpatch-a864ed67ebd0 > > Best regards, > -- > Justin Stitt <[email protected]> >
