On Mon, Sep 04, 2017 at 02:55:24PM -0700, Michael Lyle wrote:
> Most importantly, solve a crash where %llu was used to format signed
> numbers. This would cause a buffer overflow when reading sysfs
> writeback_rate_debug, as only 20 bytes were allocated for this and
> %llu writes 20 characters plus a null.
>
> Always use the units mechanism rather than having different output
> paths for simplicity.
>
> Also, correct problems with display output where 1.10 was a larger
> number than 1.09, by multiplying by 10 and then dividing by 1024 instead
> of dividing by 100. (Remainders of >= 1000 would print as .10).
>
> Minor changes: Always display the decimal point instead of trying to
> omit it based on number of digits shown. Decide what units to use
> based on 1000 as a threshold, not 1024 (in other words, always print
> at most 3 digits before the decimal point).
>
> Signed-off-by: Michael Lyle <mlyle@xxxxxxxx>
> Reported-by: Dmitry Yu Okunev <dyokunev@xxxxxxxxxxx>
Acked-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> ---
> drivers/md/bcache/util.c | 50 +++++++++++++++++++++++++++++++++---------------
> 1 file changed, 35 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> index 8c3a938f4bf0..176d3c2ef5f5 100644
> --- a/drivers/md/bcache/util.c
> +++ b/drivers/md/bcache/util.c
> @@ -74,24 +74,44 @@ STRTO_H(strtouint, unsigned int)
> STRTO_H(strtoll, long long)
> STRTO_H(strtoull, unsigned long long)
>
> +/**
> + * bch_hprint() - formats @v to human readable string for sysfs.
> + *
> + * @v - signed 64 bit integer
> + * @buf - the (at least 8 byte) buffer to format the result into.
> + *
> + * Returns the number of bytes used by format.
> + */
> ssize_t bch_hprint(char *buf, int64_t v)
> {
> static const char units[] = "?kMGTPEZY";
> - char dec[4] = "";
> - int u, t = 0;
> -
> - for (u = 0; v >= 1024 || v <= -1024; u++) {
> - t = v & ~(~0 << 10);
> - v >>= 10;
> - }
> -
> - if (!u)
> - return sprintf(buf, "%llu", v);
> -
> - if (v < 100 && v > -100)
> - snprintf(dec, sizeof(dec), ".%i", t / 100);
> -
> - return sprintf(buf, "%lli%s%c", v, dec, units[u]);
> + int u = 0, t;
> +
> + uint64_t q;
> +
> + if (v < 0)
> + q = -v;
> + else
> + q = v;
> +
> + /* For as long as the number is more than 3 digits, but at least
> + * once, shift right / divide by 1024. Keep the remainder for
> + * a digit after the decimal point.
> + */
> + do {
> + u++;
> +
> + t = q & ~(~0 << 10);
> + q >>= 10;
> + } while (q >= 1000);
> +
> + if (v < 0)
> + /* '-', up to 3 digits, '.', 1 digit, 1 character, null;
> + * yields 8 bytes.
> + */
> + return sprintf(buf, "-%llu.%i%c", q, t * 10 / 1024, units[u]);
> + else
> + return sprintf(buf, "%llu.%i%c", q, t * 10 / 1024, units[u]);
> }
>
> ssize_t bch_snprint_string_list(char *buf, size_t size, const char * const list[],
> --
> 2.11.0
>
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