Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 23 Apr 2024 10:17:09 +0200 | Subject | Re: [PATCH v5] checkpatch: add check for snprintf to scnprintf | From | Christophe JAILLET <> |
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Le 22/04/2024 à 23:33, Justin Stitt a écrit : > 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 <fthain@linux-m68k.org> > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > Changes in v5: > - use capture groups to let the user know which variation they used > - Link to v4: https://lore.kernel.org/r/20240408-snprintf-checkpatch-v4-1-8697c96ac94b@google.com > > Changes in v4: > - also check for vsnprintf variant (thanks Bill) > - Link to v3: https://lore.kernel.org/r/20240315-snprintf-checkpatch-v3-1-a451e7664306@google.com > > Changes in v3: > - fix indentation > - add reference link (https://github.com/KSPP/linux/issues/105) (thanks Joe) > - Link to v2: https://lore.kernel.org/r/20240221-snprintf-checkpatch-v2-1-9baeb59dae30@google.com > > Changes in v2: > - Had a vim moment and deleted a character before sending the patch. > - Replaced the character :) > - Link to v1: https://lore.kernel.org/r/20240221-snprintf-checkpatch-v1-1-3ac5025b5961@google.com > --- > From a discussion here [1]. > > [1]: https://lore.kernel.org/all/0f9c95f9-2c14-eee6-7faf-635880edcea4@linux-m68k.org/ > --- > scripts/checkpatch.pl | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 9c4c4a61bc83..b7404e53c554 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" . $herecurr); > } > > +# {v}snprintf uses that should likely be {v}scnprintf > + if ($line =~ /\b((v|)snprintf\s*\()/) {
Nit: I think that /\b((v|)snprintf)\s*\(/) would be nice. Otherwise, <spaces>( would be added to the message.
CJ
> + WARN("SNPRINTF", > + "Prefer ${2}scnprintf over $1 - see: https://github.com/KSPP/linux/issues/105\n" . $herecurr); > + } > + > # ethtool_sprintf uses that should likely be ethtool_puts > if ($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 <justinstitt@google.com> > > >
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