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Don't read invalid floating-point numbers in *scanf()

Browse source 
Currently, we just ignore any errors from `strtod()`. They can
happen either because no valid float can be parsed at all, or
because the state machine recognizes only a prefix of a valid
floating-point number.

Fix this by making sure `strtod()` parses everything we recognized,
provided it's non-empty. This requires to pop the last character
off the FP buffer, which is supposed to be parsed by the next
`*scanf()` directive.
This commit is contained in:
Ivan Komarov 2024-02-18 02:16:19 +01:00
parent 5fa42012da
commit e5d877ba4f
2 changed files with 40 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

29
libc/stdio/vcscanf.c
View file

@ -50,6 +50,12 @@
} \
c; \
})
#define UNBUFFER \
({ \
if (c != -1) { \
fpbuf[--fpbufcur] = '\0'; \
} \
})
/**
* String / file / stream decoder.
@ -369,10 +375,11 @@ int __vcscanf(int callback(void *), //
}
} while ((c = BUFFER) != -1 && c != ')');
if (c == ')') {
c = BUFFER;
c = READ;
}
goto GotFloatingPointNumber;
} else {
UNBUFFER;
goto GotFloatingPointNumber;
}
} else {
@ -410,6 +417,7 @@ int __vcscanf(int callback(void *), //
goto Done;
}
} else {
UNBUFFER;
goto GotFloatingPointNumber;
}
} else {
@ -462,10 +470,24 @@ int __vcscanf(int callback(void *), //
Continue:
continue;
Break:
UNBUFFER;
break;
} while ((c = BUFFER) != -1);
GotFloatingPointNumber:
fp = strtod((char *)fpbuf, NULL);
/* An empty buffer can't be a valid float; don't even bother parsing. */
bool valid = fpbufcur > 0;
if (valid) {
char *ep;
fp = strtod((char *)fpbuf, &ep);
/* We should have parsed the whole buffer. */
valid = ep == (char *)fpbuf + fpbufcur;
}
free(fpbuf);
fpbuf = NULL;
fpbufcur = fpbufsize = 0;
if (!valid) {
goto Done;
}
if (!discard) {
++items;
void *out = va_arg(va, void *);
@ -475,9 +497,6 @@ int __vcscanf(int callback(void *), //
*(double *)out = (double)fp;
}
}
free(fpbuf);
fpbuf = NULL;
fpbufcur = fpbufsize = 0;
continue;
ReportConsumed:
n_ptr = va_arg(va, int *);

24
test/libc/stdio/sscanf_test.c
View file

@ -394,6 +394,20 @@ TEST(sscanf, floating_point_infinity_double_precision) {
EXPECT_TRUE(isinf(g));
}
TEST(sscanf, floating_point_invalid) {
float dummy;
EXPECT_EQ(0, sscanf("junk", "%f", &dummy));
EXPECT_EQ(0, sscanf("e9", "%f", &dummy));
EXPECT_EQ(0, sscanf("-e9", "%f", &dummy));
}
TEST(sscanf, floating_point_invalid_double_precision) {
double dummy;
EXPECT_EQ(0, sscanf("junk", "%lf", &dummy));
EXPECT_EQ(0, sscanf("e9", "%lf", &dummy));
EXPECT_EQ(0, sscanf("-e9", "%lf", &dummy));
}
TEST(sscanf, floating_point_documentation_examples) {
float a = 666.666f, b = a, c = b, d = c, e = d, f = e, g = f, h = g, i = h,
j = i;
@ -401,7 +415,7 @@ TEST(sscanf, floating_point_documentation_examples) {
EXPECT_EQ(2, sscanf("111.11 -2.22", "%f %f", &a, &b));
EXPECT_EQ(3, sscanf("Nan nan(2) inF", "%f %f %f", &c, &d, &e));
EXPECT_EQ(
5, sscanf("0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz -0.0000000123junk junk",
2, sscanf("0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz -0.0000000123junk junk",
"%f %f %f %f %f", &f, &g, &h, &i, &j));
EXPECT_EQ(111.11f, a);
@ -411,9 +425,6 @@ TEST(sscanf, floating_point_documentation_examples) {
EXPECT_TRUE(isinf(e));
EXPECT_EQ(0X1.BC70A3D70A3D7P+6f, f);
EXPECT_TRUE(isinf(g));
EXPECT_EQ(-0.0000000123f, h);
EXPECT_EQ(.0f, i);
EXPECT_EQ(.0f, j);
}
TEST(sscanf, floating_point_documentation_examples_double_precision) {
@ -423,7 +434,7 @@ TEST(sscanf, floating_point_documentation_examples_double_precision) {
EXPECT_EQ(2, sscanf("111.11 -2.22", "%lf %lf", &a, &b));
EXPECT_EQ(3, sscanf("Nan nan(2) inF", "%lf %lf %lf", &c, &d, &e));
EXPECT_EQ(
5, sscanf("0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz -0.0000000123junk junk",
2, sscanf("0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz -0.0000000123junk junk",
"%lf %lf %lf %lf %lf", &f, &g, &h, &i, &j));
EXPECT_EQ(111.11, a);
@ -433,9 +444,6 @@ TEST(sscanf, floating_point_documentation_examples_double_precision) {
EXPECT_TRUE(isinf(e));
EXPECT_EQ(0X1.BC70A3D70A3D7P+6, f);
EXPECT_TRUE(isinf(g));
EXPECT_EQ(-0.0000000123, h);
EXPECT_EQ(.0, i);
EXPECT_EQ(.0, j);
}
TEST(sscanf, luplus) {