From 42cc08d13ab8e68f76882b216da0b28d06f29e11 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 22 May 2023 14:04:41 -0500 Subject: [PATCH] cutils: Improve qemu_strtosz handling of fractions We have several limitations and bugs worth fixing; they are inter-related enough that it is not worth splitting this patch into smaller pieces: * ".5k" should work to specify 512, just as "0.5k" does * "1.9999k" and "1." + "9"*50 + "k" should both produce the same result of 2048 after rounding * "1." + "0"*350 + "1B" should not be treated the same as "1.0B"; underflow in the fraction should not be lost * "7.99e99" and "7.99e999" look similar, but our code was doing a read-out-of-bounds on the latter because it was not expecting ERANGE due to overflow. While we document that scientific notation is not supported, and the previous patch actually fixed qemu_strtod_finite() to no longer return ERANGE overflows, it is easier to pre-filter than to try and determine after the fact if strtod() consumed more than we wanted. Note that this is a low-level semantic change (when endptr is not NULL, we can now successfully parse with a scale of 'E' and then report trailing junk, instead of failing outright with EINVAL); but an earlier commit already argued that this is not a high-level semantic change since the only caller passing in a non-NULL endptr also checks that the tail is whitespace-only. Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1629 Fixes: cf923b78 ("utils: Improve qemu_strtosz() to have 64 bits of precision", 6.0.0) Fixes: 7625a1ed ("utils: Use fixed-point arithmetic in qemu_strtosz", 6.0.0) Signed-off-by: Eric Blake Reviewed-by: Hanna Czenczek Message-Id: <20230522190441.64278-20-eblake@redhat.com> [eblake: tweak function comment for accuracy] --- tests/unit/test-cutils.c | 50 +++++++++------------- util/cutils.c | 92 ++++++++++++++++++++++++++++++---------- 2 files changed, 88 insertions(+), 54 deletions(-) diff --git a/tests/unit/test-cutils.c b/tests/unit/test-cutils.c index 1ee410fae4..227acc5995 100644 --- a/tests/unit/test-cutils.c +++ b/tests/unit/test-cutils.c @@ -3408,19 +3408,18 @@ static void test_qemu_strtosz_float(void) /* An empty fraction tail is tolerated */ do_strtosz("1.k", 0, 1024, 3); - /* FIXME An empty fraction head should be tolerated */ - do_strtosz(" .5k", -EINVAL /* FIXME 0 */, 0 /* FIXME 512 */, - 0 /* FIXME 4 */); + /* An empty fraction head is tolerated */ + do_strtosz(" .5k", 0, 512, 4); /* For convenience, we permit values that are not byte-exact */ do_strtosz("12.345M", 0, (uint64_t) (12.345 * MiB + 0.5), 7); - /* FIXME Fraction tail should round correctly */ + /* Fraction tail can round up */ do_strtosz("1.9999k", 0, 2048, 7); do_strtosz("1.9999999999999999999999999999999999999999999999999999k", 0, - 1024 /* FIXME 2048 */, 55); + 2048, 55); - /* FIXME ERANGE underflow in the fraction tail should not matter for 'k' */ + /* ERANGE underflow in the fraction tail does not matter for 'k' */ do_strtosz("1." "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" @@ -3429,7 +3428,7 @@ static void test_qemu_strtosz_float(void) "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" - "1k", 0, 1 /* FIXME 1024 */, 354); + "1k", 0, 1024, 354); } static void test_qemu_strtosz_invalid(void) @@ -3453,10 +3452,9 @@ static void test_qemu_strtosz_invalid(void) do_strtosz("1.1B", -EINVAL, 0, 0); do_strtosz("1.1", -EINVAL, 0, 0); - /* FIXME underflow in the fraction tail should matter for 'B' */ + /* 'B' cannot have any nonzero fraction, even with rounding or underflow */ do_strtosz("1.00001B", -EINVAL, 0, 0); - do_strtosz("1.00000000000000000001B", 0 /* FIXME -EINVAL */, - 1 /* FIXME 0 */, 23 /* FIXME 0 */); + do_strtosz("1.00000000000000000001B", -EINVAL, 0, 0); do_strtosz("1." "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" @@ -3465,8 +3463,7 @@ static void test_qemu_strtosz_invalid(void) "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" - "1B", 0 /* FIXME -EINVAL */, 1 /* FIXME 0 */, - 354 /* FIXME 0 */); + "1B", -EINVAL, 0, 0); /* No hex fractions */ do_strtosz("0x1.8k", -EINVAL, 0, 0); @@ -3512,28 +3509,20 @@ static void test_qemu_strtosz_trailing(void) do_strtosz_full("123-45", qemu_strtosz, 0, 123, 3, -EINVAL, 0); do_strtosz_full(" 123 - 45", qemu_strtosz, 0, 123, 4, -EINVAL, 0); - /* FIXME should stop parse after 'e'. No floating point exponents */ - do_strtosz_full("1.5e1k", qemu_strtosz, -EINVAL /* FIXME 0 */, - 0 /* FIXME EiB * 1.5 */, 0 /* FIXME 4 */, - -EINVAL, 0); - do_strtosz_full("1.5E+0k", qemu_strtosz, -EINVAL /* FIXME 0 */, - 0 /* FIXME EiB * 1.5 */, 0 /* FIXME 4 */, - -EINVAL, 0); - - /* FIXME overflow in fraction is still buggy */ - do_strtosz_full("1.5E999", qemu_strtosz, 0, 1 /* FIXME EiB * 1.5 */, - 2 /* FIXME 4 */, -EINVAL, 0); + /* Parse stops at 'e', which is not a floating point exponent */ + do_strtosz_full("1.5e1k", qemu_strtosz, 0, EiB * 1.5, 4, -EINVAL, 0); + do_strtosz_full("1.5E+0k", qemu_strtosz, 0, EiB * 1.5, 4, -EINVAL, 0); + do_strtosz_full("1.5E999", qemu_strtosz, 0, EiB * 1.5, 4, -EINVAL, 0); } static void test_qemu_strtosz_erange(void) { - /* FIXME negative values fit better as ERANGE */ + /* no negative values */ do_strtosz(" -0", -ERANGE, 0, 3); do_strtosz("-1", -ERANGE, 0, 2); do_strtosz_full("-2M", qemu_strtosz, -ERANGE, 0, 2, -EINVAL, 0); - do_strtosz(" -.0", -EINVAL /* FIXME -ERANGE */, 0, 0 /* FIXME 4 */); - do_strtosz_full("-.1k", qemu_strtosz, -EINVAL /* FIXME -ERANGE */, 0, - 0 /* FIXME 3 */, -EINVAL, 0); + do_strtosz(" -.0", -ERANGE, 0, 4); + do_strtosz_full("-.1k", qemu_strtosz, -ERANGE, 0, 3, -EINVAL, 0); do_strtosz_full(" -." "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" @@ -3542,17 +3531,16 @@ static void test_qemu_strtosz_erange(void) "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" "00000000000000000000000000000000000000000000000000" - "1M", qemu_strtosz, -EINVAL /* FIXME -ERANGE */, 0, - 0 /* FIXME 354 */, -EINVAL, 0); + "1M", qemu_strtosz, -ERANGE, 0, 354, -EINVAL, 0); /* 2^64; see strtosz_simple for 2^64-1 */ do_strtosz("18446744073709551616", -ERANGE, 0, 20); do_strtosz("20E", -ERANGE, 0, 3); - /* FIXME Fraction tail can cause ERANGE overflow */ + /* Fraction tail can cause ERANGE overflow */ do_strtosz("15.9999999999999999999999999999999999999999999999999999E", - 0 /* FIXME -ERANGE */, 15ULL * EiB /* FIXME 0 */, 56); + -ERANGE, 0, 56); /* EINVAL has priority over ERANGE */ do_strtosz_full("100000Pjunk", qemu_strtosz, -ERANGE, 0, 7, -EINVAL, 0); diff --git a/util/cutils.c b/util/cutils.c index bde2da59bd..25373198ad 100644 --- a/util/cutils.c +++ b/util/cutils.c @@ -194,15 +194,19 @@ static int64_t suffix_mul(char suffix, int64_t unit) * - 12345 - decimal, scale determined by @default_suffix and @unit * - 12345{bBkKmMgGtTpPeE} - decimal, scale determined by suffix and @unit * - 12345.678{kKmMgGtTpPeE} - decimal, scale determined by suffix, and - * fractional portion is truncated to byte + * fractional portion is truncated to byte, either side of . may be empty * - 0x7fEE - hexadecimal, unit determined by @default_suffix * * The following are intentionally not supported - * - hex with scaling suffix, such as 0x20M - * - octal, such as 08 - * - fractional hex, such as 0x1.8 - * - negative values, including -0 - * - floating point exponents, such as 1e3 + * - hex with scaling suffix, such as 0x20M or 0x1p3 (both fail with + * -EINVAL), while 0x1b is 27 (not 1 with byte scale) + * - octal, such as 08 (parsed as decimal instead) + * - binary, such as 0b1000 (parsed as 0b with trailing garbage "1000") + * - fractional hex, such as 0x1.8 (parsed as 0 with trailing garbage "x1.8") + * - negative values, including -0 (fail with -ERANGE) + * - floating point exponents, such as 1e3 (parsed as 1e with trailing + * garbage "3") or 0x1p3 (rejected as hex with scaling suffix) + * - non-finite values, such as inf or NaN (fail with -EINVAL) * * The end pointer will be returned in *end, if not NULL. If there is * no fraction, the input can be decimal or hexadecimal; if there is a @@ -221,17 +225,17 @@ static int do_strtosz(const char *nptr, const char **end, uint64_t *result) { int retval; - const char *endptr, *f; + const char *endptr; unsigned char c; - uint64_t val, valf = 0; + uint64_t val = 0, valf = 0; int64_t mul; /* Parse integral portion as decimal. */ retval = parse_uint(nptr, &endptr, 10, &val); - if (retval) { + if (retval == -ERANGE || !nptr) { goto out; } - if (val == 0 && (*endptr == 'x' || *endptr == 'X')) { + if (retval == 0 && val == 0 && (*endptr == 'x' || *endptr == 'X')) { /* Input looks like hex; reparse, and insist on no fraction or suffix. */ retval = qemu_strtou64(nptr, &endptr, 16, &val); if (retval) { @@ -242,26 +246,68 @@ static int do_strtosz(const char *nptr, const char **end, retval = -EINVAL; goto out; } - } else if (*endptr == '.') { + } else if (*endptr == '.' || (endptr == nptr && strchr(nptr, '.'))) { /* * Input looks like a fraction. Make sure even 1.k works - * without fractional digits. If we see an exponent, treat - * the entire input as invalid instead. + * without fractional digits. strtod tries to treat 'e' as an + * exponent, but we want to treat it as a scaling suffix; + * doing this requires modifying a copy of the fraction. */ - double fraction; + double fraction = 0.0; - f = endptr; - retval = qemu_strtod_finite(f, &endptr, &fraction); - if (retval) { + if (retval == 0 && *endptr == '.' && !isdigit(endptr[1])) { + /* If we got here, we parsed at least one digit already. */ endptr++; - } else if (memchr(f, 'e', endptr - f) || memchr(f, 'E', endptr - f)) { - endptr = nptr; - retval = -EINVAL; - goto out; } else { - /* Extract into a 64-bit fixed-point fraction. */ - valf = (uint64_t)(fraction * 0x1p64); + char *e; + const char *tail; + g_autofree char *copy = g_strdup(endptr); + + e = strchr(copy, 'e'); + if (e) { + *e = '\0'; + } + e = strchr(copy, 'E'); + if (e) { + *e = '\0'; + } + /* + * If this is a floating point, we are guaranteed that '.' + * appears before any possible digits in copy. If it is + * not a floating point, strtod will fail. Either way, + * there is now no exponent in copy, so if it parses, we + * know 0.0 <= abs(result) <= 1.0 (after rounding), and + * ERANGE is only possible on underflow which is okay. + */ + retval = qemu_strtod_finite(copy, &tail, &fraction); + endptr += tail - copy; + if (signbit(fraction)) { + retval = -ERANGE; + goto out; + } } + + /* Extract into a 64-bit fixed-point fraction. */ + if (fraction == 1.0) { + if (val == UINT64_MAX) { + retval = -ERANGE; + goto out; + } + val++; + } else if (retval == -ERANGE) { + /* See comments above about underflow */ + valf = 1; + retval = 0; + } else { + /* We want non-zero valf for any non-zero fraction */ + valf = (uint64_t)(fraction * 0x1p64); + if (valf == 0 && fraction > 0.0) { + valf = 1; + } + } + } + if (retval) { + goto out; } c = *endptr; mul = suffix_mul(c, unit);