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Fix an infinite loop in time2sub.

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The problem is that time_t is signed, and the original code relied on the
fact that (X + c < X) in case of overflow for c >= 0. Unfortunately, this
condition is only guaranteed by the standard for unsigned arithmetic, and
the gcc 4.4.0 optimizer did completely remove the corresponding test from
the code. This resulted in a missing boundary check, and an infinite loop.

The problem is solved by testing explicitely for TIME_T_MIN and TIME_T_MAX
in the loop that uses this.

Also fix increment_overflow and long_increment_overflow which were buggy
for exactly the same reasons.

Also remove some compiler warnings.

Note: a similar fix was performed in bionic/libc
This commit is contained in:
David 'Digit' Turner 2009-09-09 18:32:07 -07:00
parent 82a6014d90
commit 833ea8d502
1 changed files with 53 additions and 18 deletions
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71
libcutils/tztime.c
View file

@ -53,6 +53,31 @@ static char elsieid[] = "@(#)localtime.c 8.3";
#define OPEN_MODE O_RDONLY
#endif /* !defined O_BINARY */
/* Complex computations to determine the min/max of time_t depending
* on TYPE_BIT / TYPE_SIGNED / TYPE_INTEGRAL.
* These macros cannot be used in pre-processor directives, so we
* let the C compiler do the work, which makes things a bit funky.
*/
static const time_t TIME_T_MAX =
TYPE_INTEGRAL(time_t) ?
( TYPE_SIGNED(time_t) ?
~((time_t)1 << (TYPE_BIT(time_t)-1))
:
~(time_t)0
)
: /* if time_t is a floating point number */
( sizeof(time_t) > sizeof(float) ? (time_t)DBL_MAX : (time_t)FLT_MAX );
static const time_t TIME_T_MIN =
TYPE_INTEGRAL(time_t) ?
( TYPE_SIGNED(time_t) ?
((time_t)1 << (TYPE_BIT(time_t)-1))
:
0
)
:
( sizeof(time_t) > sizeof(float) ? (time_t)DBL_MIN : (time_t)FLT_MIN );
#ifndef WILDABBR
/*
** Someone might make incorrect use of a time zone abbreviation:
@ -158,7 +183,7 @@ static void gmtload P((struct state * sp));
static struct tm * gmtsub P((const time_t * timep, long offset,
struct tm * tmp));
static struct tm * localsub P((const time_t * timep, long offset,
struct tm * tmp, struct state *sp));
struct tm * tmp, const struct state *sp));
static int increment_overflow P((int * number, int delta));
static int leaps_thru_end_of P((int y));
static int long_increment_overflow P((long * number, int delta));
@ -1157,7 +1182,7 @@ localsub(timep, offset, tmp, sp)
const time_t * const timep;
const long offset;
struct tm * const tmp;
struct state * sp;
const struct state * sp;
{
register const struct ttinfo * ttisp;
register int i;
@ -1553,26 +1578,36 @@ char * buf;
static int
increment_overflow(number, delta)
int * number;
int delta;
int * number;
int delta;
{
int number0;
unsigned number0 = (unsigned)*number;
unsigned number1 = (unsigned)(number0 + delta);
number0 = *number;
*number += delta;
return (*number < number0) != (delta < 0);
*number = (int)number1;
if (delta >= 0) {
return ((int)number1 < (int)number0);
} else {
return ((int)number1 > (int)number0);
}
}
static int
long_increment_overflow(number, delta)
long * number;
int delta;
long * number;
int delta;
{
long number0;
unsigned long number0 = (unsigned long)*number;
unsigned long number1 = (unsigned long)(number0 + delta);
number0 = *number;
*number += delta;
return (*number < number0) != (delta < 0);
*number = (long)number1;
if (delta >= 0) {
return ((long)number1 < (long)number0);
} else {
return ((long)number1 > (long)number0);
}
}
static int
@ -1741,14 +1776,14 @@ const struct state * sp;
} else dir = tmcomp(&mytm, &yourtm);
if (dir != 0) {
if (t == lo) {
if (t == TIME_T_MAX)
return WRONG;
++t;
if (t <= lo)
return WRONG;
++lo;
} else if (t == hi) {
if (t == TIME_T_MIN)
return WRONG;
--t;
if (t >= hi)
return WRONG;
--hi;
}
if (lo > hi)