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ICU-13834 add pinCapacity() for safer output buffer capacity checking. (#105)

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* ICU-13834 add pinCapacity() for safer output buffer capacity checking.

* ICU-13834 pinCapacity, fix typo in comment.
This commit is contained in:
Andy Heninger 2018-09-07 13:42:21 -07:00 • committed by Shane Carr
parent 82f0f480d4
commit 71c66bbb0b
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2 changed files with 45 additions and 10 deletions
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43
icu4c/source/common/putilimp.h
View file

@ -574,6 +574,49 @@ U_INTERNAL void * U_EXPORT2 uprv_maximumPtr(void *base);
# endif
#endif
#ifdef __cplusplus
/**
* Pin a buffer capacity such that doing pointer arithmetic
* on the destination pointer and capacity cannot overflow.
*
* The pinned capacity must fulfill the following conditions (for positive capacities):
* - dest + capacity is a valid pointer according to the machine arcitecture (AS/400, 64-bit, etc.)
* - (dest + capacity) >= dest
* - The size (in bytes) of T[capacity] does not exceed 0x7fffffff
*
* @param dest the destination buffer pointer.
* @param capacity the requested buffer capacity, in units of type T.
* @return the pinned capacity.
* @internal
*/
template <typename T>
inline int32_t pinCapacity(T *dest, int32_t capacity) {
if (capacity <= 0) { return capacity; }
uintptr_t destInt = (uintptr_t)dest;
uintptr_t maxInt;
# if U_PLATFORM == U_PF_OS390 && !defined(_LP64)
// We have 31-bit pointers.
maxInt = 0x7fffffff;
# elif U_PLATFORM == U_PF_OS400
maxInt = (uintptr_t)uprv_maximumPtr((void *)dest);
# else
maxInt = destInt + 0x7fffffffu;
if (maxInt < destInt) {
// Less than 2GB to the end of the address space.
// Pin to that to prevent address overflow.
maxInt = (uintptr_t)-1;
}
# endif
uintptr_t maxBytes = maxInt - destInt; // max. 2GB
int32_t maxCapacity = (int32_t)(maxBytes / sizeof(T));
return capacity <= maxCapacity ? capacity : maxCapacity;
}
#endif // __cplusplus
/* Dynamic Library Functions */
typedef void (UVoidFunction)(void);

12
icu4c/source/common/ucnv.cpp
View file

@ -1743,13 +1743,9 @@ ucnv_fromUChars(UConverter *cnv,
}
if(srcLength>0) {
srcLimit=src+srcLength;
destCapacity=pinCapacity(dest, destCapacity);
destLimit=dest+destCapacity;
/* pin the destination limit to U_MAX_PTR; NULL check is for OS/400 */
if(destLimit<dest || (destLimit==NULL && dest!=NULL)) {
destLimit=(char *)U_MAX_PTR(dest);
}
/* perform the conversion */
ucnv_fromUnicode(cnv, &dest, destLimit, &src, srcLimit, 0, TRUE, pErrorCode);
destLength=(int32_t)(dest-originalDest);
@ -1803,13 +1799,9 @@ ucnv_toUChars(UConverter *cnv,
}
if(srcLength>0) {
srcLimit=src+srcLength;
destCapacity=pinCapacity(dest, destCapacity);
destLimit=dest+destCapacity;
/* pin the destination limit to U_MAX_PTR; NULL check is for OS/400 */
if(destLimit<dest || (destLimit==NULL && dest!=NULL)) {
destLimit=(UChar *)U_MAX_PTR(dest);
}
/* perform the conversion */
ucnv_toUnicode(cnv, &dest, destLimit, &src, srcLimit, 0, TRUE, pErrorCode);
destLength=(int32_t)(dest-originalDest);