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Remove UBSAN issues discovered via fuzzing tests.

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The arithmetic conversions in C say that if a binary operator has an
unsigned and signed type as operands and the unsigned type has a greater
rank then the signed value is converted to unsigned.  This is bad if the
signed value is negative.

There are a few places in the code which have this situation; convert
the signed value to positive and add instead of subtracting.

Reported by He Jingxuan <jingxuan.he@inf.ethz.ch>

* src/read.c (find_map_unquote): Use a positive int in memmove().
(find_char_unquote): Ditto.
(find_percent_cached): Ditto.
This commit is contained in:
Paul Smith 2021-09-06 00:14:57 -04:00
parent cc6dc70b16
commit abb1e8d10b
1 changed files with 18 additions and 6 deletions
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24
src/read.c
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@ -2354,8 +2354,12 @@ find_map_unquote (char *string, int stopmap)
string_len = strlen (string);
/* The number of backslashes is now -I.
Copy P over itself to swallow half of them. */
memmove (&p[i], &p[i/2], (string_len - (p - string)) - (i/2) + 1);
p += i/2;
{
/* Avoid arithmetic conversion of negative values to unsigned. */
int hi = -(i/2);
memmove (&p[i], &p[i/2], (string_len - (p - string)) + hi + 1);
p += i/2;
}
if (i % 2 == 0)
/* All the backslashes quoted each other; the STOPCHAR was
unquoted. */
@ -2397,8 +2401,12 @@ find_char_unquote (char *string, int stop)
string_len = strlen (string);
/* The number of backslashes is now -I.
Copy P over itself to swallow half of them. */
memmove (&p[i], &p[i/2], (string_len - (p - string)) - (i/2) + 1);
p += i/2;
{
/* Avoid arithmetic conversion of negative values to unsigned. */
int hi = -(i/2);
memmove (&p[i], &p[i/2], (string_len - (p - string)) + hi + 1);
p += i/2;
}
if (i % 2 == 0)
/* All the backslashes quoted each other; the STOPCHAR was
unquoted. */
@ -2523,8 +2531,12 @@ find_percent_cached (const char **string)
/* The number of backslashes is now -I.
Copy P over itself to swallow half of them. */
memmove (&pv[i], &pv[i/2], (slen - (pv - new)) - (i/2) + 1);
p += i/2;
{
/* Avoid arithmetic conversion of negative values to unsigned. */
int hi = -(i/2);
memmove (&pv[i], &pv[i/2], (slen - (pv - new)) + hi + 1);
p += i/2;
}
/* If the backslashes quoted each other; the % was unquoted. */
if (i % 2 == 0)