| Message ID | 20240315-snprintf-checkpatch-v3-1-a451e7664306@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v3] checkpatch: add check for snprintf to scnprintf | expand |
On Fri, Mar 15, 2024 at 1:09 PM Justin Stitt <justinstitt@google.com> 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 <fthain@linux-m68k.org> > Signed-off-by: Justin Stitt <justinstitt@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..69dfb7412014 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 =~ /\bsnprintf\s*\(\s*/) { Should this check for the 'vsnprintf' variant as well? -bw > + WARN("SNPRINTF", > + "Prefer scnprintf over snprintf - 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> > >
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 9c4c4a61bc83..69dfb7412014 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 =~ /\bsnprintf\s*\(\s*/) { + WARN("SNPRINTF", + "Prefer scnprintf over snprintf - 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",
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 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(+) --- base-commit: b401b621758e46812da61fa58a67c3fd8d91de0d change-id: 20240221-snprintf-checkpatch-a864ed67ebd0 Best regards, -- Justin Stitt <justinstitt@google.com>