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Commit 9276717b authored by Michael Lyle's avatar Michael Lyle Committed by Jens Axboe
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bcache: fix bch_hprint crash and improve output 



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: default avatarMichael Lyle <mlyle@lyle.org>
Reported-by: default avatarDmitry Yu Okunev <dyokunev@ut.mephi.ru>
Acked-by: default avatarKent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: default avatarColy Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7b6a8570

drivers/md/bcache/util.c

+35 −15
Original line number Diff line number Diff line
@@ -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;

	int u = 0, t;



	for (u = 0; v >= 1024 || v <= -1024; u++) {

		t = v & ~(~0 << 10);

		v >>= 10;

	}

	uint64_t q;



	if (!u)

		return sprintf(buf, "%llu", v);

	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++;



	if (v < 100 && v > -100)

		snprintf(dec, sizeof(dec), ".%i", t / 100);

		t = q & ~(~0 << 10);

		q >>= 10;

	} while (q >= 1000);



	return sprintf(buf, "%lli%s%c", v, dec, units[u]);

	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[],