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Re: [PATCH 06/14] lib/vsprintf.c: warn about too large precisions and field widths

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On Mon, Nov 23 2015, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Mon, Nov 23, 2015 at 11:29 PM, Rasmus Villemoes
> <linux@rasmusvillemoes.dk> wrote:
>> The field width is overloaded to pass some extra information for
>> some %p extensions (e.g. #bits for %pb). But we might silently
>> truncate the passed value when we stash it in struct printf_spec (see
>> e.g. "lib/vsprintf.c: expand field_width to 24 bits").  Hopefully 23
>> value bits should now be enough for everybody, but if not, let's make
>> some noise.
>>
>> Do the same for the precision. In both cases, clamping seems more
>> sensible than truncating. While, according to POSIX, "A negative
>> precision is taken as if the precision were omitted.", the kernel's
>> printf has always treated that case as if the precision was 0, so we
>> use that as lower bound. For the field width, the smallest
>> representable value is actually -(1<<23), but a negative field width
>> means 'set the LEFT flag and use the absolute value', so we want the
>> absolute value to fit.
>>
>
> Do we need to do the same for bstr_printf() ?
>

Heh, apparently I didn't learn anything from 762abb51. Thanks, will fix
in next spin.

Rasmus
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Thread

[PATCH 00/14] printf stuff for 4.5 Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
  [PATCH 14/14] lib/test_printf.c: test dentry printing Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
  [PATCH 02/14] lib/vsprintf.c: move string() below widen_string() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
  [PATCH 03/14] lib/vsprintf.c: eliminate potential race in string() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
    Re: [PATCH 03/14] lib/vsprintf.c: eliminate potential race in string() Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-24 00:00 +0100
      Re: [PATCH 03/14] lib/vsprintf.c: eliminate potential race in string() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-26 22:40 +0100
  [PATCH 12/14] lib/test_printf.c: account for kvasprintf tests Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
  [PATCH 06/14] lib/vsprintf.c: warn about too large precisions and field widths Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
    Re: [PATCH 06/14] lib/vsprintf.c: warn about too large precisions and  field widths Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-23 23:40 +0100
      Re: [PATCH 06/14] lib/vsprintf.c: warn about too large precisions and field widths Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-26 22:20 +0100
  [PATCH 07/14] lib/vsprintf.c: slightly refactor vscnprintf() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
    Re: [PATCH 07/14] lib/vsprintf.c: slightly refactor vscnprintf() Andy Shevchenko <andy.shevchenko@gmail.com> - 2015-11-23 23:40 +0100
      Re: [PATCH 07/14] lib/vsprintf.c: slightly refactor vscnprintf() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-26 22:30 +0100
  [PATCH 11/14] lib/test_printf.c: test precision quirks Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100
  [PATCH 10/14] lib/test_printf.c: check for out-of-bound writes Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-11-23 22:40 +0100

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