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Date: Mon, 21 Dec 2020 16:16:01 +0100 From: Petr Mladek <pmladek@...e.com> To: Richard Fitzgerald <rf@...nsource.cirrus.com> Cc: rostedt@...dmis.org, sergey.senozhatsky@...il.com, shuah@...nel.org, patches@...nsource.cirrus.com, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, Stanislaw Gruszka <stf_xl@...pl>, Kalle Valo <kvalo@...eaurora.org>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, linux-wireless@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH v3 1/4] lib: vsprintf: scanf: Negative number must have field width > 1 On Thu 2020-12-17 18:00:54, Richard Fitzgerald wrote: > If a signed number field starts with a '-' the field width must be > 1, > or unlimited, to allow at least one digit after the '-'. > > This patch adds a check for this. If a signed field starts with '-' > and field_width == 1 the scanf will quit. > > It is ok for a signed number field to have a field width of 1 if it > starts with a digit. In that case the single digit can be converted. The change makes perfect sense. vsscanf() should always process only one character when the field width is 1. Well, it has a potential to break existing users that rely on the broken behavior. Fortunately, there seems be only one: drivers/net/wireless/intel/iwlegacy/3945-mac.c: if (sscanf(buf, "%1i", &ant) != 1) { It is used to set a device parameter: il3945_mod_params.antenna. There are three valid values: enum il3945_antenna { IL_ANTENNA_DIVERSITY, IL_ANTENNA_MAIN, IL_ANTENNA_AUX }; So, we should be on the safe side. Anyway, adding people from get_maintainer.pl drivers/net/wireless/intel/iwlegacy/3945-mac.c so that they are aware of this. > Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com> Reviewed-by: Petr Mladek <pmladek@...e.com> Best Regards, Petr > --- > lib/vsprintf.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 14c9a6af1b23..8954ff94a53c 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -3433,8 +3433,12 @@ int vsscanf(const char *buf, const char *fmt, va_list args) > str = skip_spaces(str); > > digit = *str; > - if (is_sign && digit == '-') > + if (is_sign && digit == '-') { > + if (field_width == 1) > + break; > + > digit = *(str + 1); > + } > > if (!digit > || (base == 16 && !isxdigit(digit)) > -- > 2.20.1
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