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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.

Note: a similar fix is needed for system/core/libcutils
This commit is contained in:
David 'Digit' Turner
2009-09-09 17:41:59 -07:00
parent b4423ff7df
commit 2093d350be
1 changed files with 47 additions and 12 deletions
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59
libc/tzcode/localtime.c
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@@ -75,6 +75,31 @@ static __inline__ void _tzUnlock(void)
pthread_mutex_unlock(&_tzMutex);
}
/* 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:
@@ -1683,11 +1708,16 @@ increment_overflow(number, 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
@@ -1695,11 +1725,16 @@ long_increment_overflow(number, 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
@@ -1868,14 +1903,14 @@ const int do_norm_secs;
} else dir = tmcomp(&mytm, &yourtm);
if (dir != 0) {
if (t == lo) {
++t;
if (t <= lo)
if (t == TIME_T_MAX)
return WRONG;
++t;
++lo;
} else if (t == hi) {
--t;
if (t >= hi)
if (t == TIME_T_MIN)
return WRONG;
--t;
--hi;
}
if (lo > hi)