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stdio: fix vfscanf with matches longer than INT_MAX (bug 27650)

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Patterns like %*[ can safely be used to match a great many characters,
and it's quite realisitic to use them for more than INT_MAX characters
from an IO stream.

With the previous approach, after INT_MAX characters (v)fscanf would
return successfully, indicating an end to the match, even though there
wasn't one.
This commit is contained in:
Alyssa Ross 2021-05-03 10:34:11 +02:00 • committed by Florian Weimer
parent c2fd60a586
commit b03e4d7bd2
1 changed files with 4 additions and 9 deletions
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13
stdio-common/vfscanf-internal.c
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@ -2479,11 +2479,6 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
else else
not_in = 0; not_in = 0;
if (width < 0)
/* There is no width given so there is also no limit on the
number of characters we read. Therefore we set width to
a very high value to make the algorithm easier. */
width = INT_MAX;
#ifdef COMPILE_WSCANF #ifdef COMPILE_WSCANF
/* Find the beginning and the end of the scanlist. We are not /* Find the beginning and the end of the scanlist. We are not
@ -2647,7 +2642,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
} }
} }
} }
while (--width > 0 && inchar () != WEOF); while ((width < 0 || --width > 0) && inchar () != WEOF);
out: out:
#else #else
char buf[MB_LEN_MAX]; char buf[MB_LEN_MAX];
@ -2732,7 +2727,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
} }
} }
if (--width <= 0) if (width >= 0 && --width <= 0)
break; break;
} }
while (inchar () != EOF); while (inchar () != EOF);
@ -2884,7 +2879,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
assert (n <= MB_LEN_MAX); assert (n <= MB_LEN_MAX);
str += n; str += n;
} }
while (--width > 0 && inchar () != WEOF); while ((width < 0 || --width > 0) && inchar () != WEOF);
out2: out2:
#else #else
do do
@ -2938,7 +2933,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
} }
} }
} }
while (--width > 0 && inchar () != EOF); while ((width < 0 || --width > 0) && inchar () != EOF);
#endif #endif
if (__glibc_unlikely (now == read_in)) if (__glibc_unlikely (now == read_in))