Bug #13595
closed
rb_alloc_tmp_buffer2 broken when: elsize % sizeof(VALUE) == 0
Added by normalperson (Eric Wong) almost 7 years ago.
Updated almost 7 years ago.
Description
Here is the function in full as of current trunk (r58863):
static inline void *
rb_alloc_tmp_buffer2(volatile VALUE *store, long count, size_t elsize)
{
size_t cnt = (size_t)count;
if (elsize % sizeof(VALUE) == 0) {
if (RB_UNLIKELY(cnt > LONG_MAX / sizeof(VALUE))) {
ruby_malloc_size_overflow(cnt, elsize);
}
}
else {
size_t size, max = LONG_MAX - sizeof(VALUE) + 1;
if (RB_UNLIKELY(rb_mul_size_overflow(cnt, elsize, max, &size))) {
ruby_malloc_size_overflow(cnt, elsize);
}
cnt = (size + sizeof(VALUE) - 1) / sizeof(VALUE);
}
return rb_alloc_tmp_buffer_with_count(store, cnt * sizeof(VALUE), cnt);
}
Notice that elsize is completely ignored in the top branch when
"(elsize % sizeof(VALUE) == 0)
" is true; this gives me problems
when attempting to use ALLOCV_N
.
I am terrible at arithmetic and this function is too complicated for me,
so I'll let naruse or someone else fix this. But please do. Thanks
normalperson@yhbt.net wrote:
Bug #13595: rb_alloc_tmp_buffer2 broken when: elsize % sizeof(VALUE) == 0
https://bugs.ruby-lang.org/issues/13595
Perhaps the following patch is what is needed:
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1611,7 +1611,7 @@ static inline void *
rb_alloc_tmp_buffer2(volatile VALUE *store, long count, size_t elsize)
{
size_t cnt = (size_t)count;
- if (elsize % sizeof(VALUE) == 0) {
+ if (elsize == sizeof(VALUE)) {
if (RB_UNLIKELY(cnt > LONG_MAX / sizeof(VALUE))) {
ruby_malloc_size_overflow(cnt, elsize);
}
...
} /* else {...} */
return rb_alloc_tmp_buffer_with_count(store, cnt * sizeof(VALUE), cnt);
Sorry; I am horrible at arithmetic. Honestly I have panic
attacks whenever I try to do it. Any help checking this
function would be greatly appreciated. Thank you.
- Description updated (diff)
Maybe like this?
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 0b277dce19..95dab1bf3f 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1612,9 +1612,10 @@ rb_alloc_tmp_buffer2(volatile VALUE *store, long count, size_t elsize)
{
size_t cnt = (size_t)count;
if (elsize % sizeof(VALUE) == 0) {
- if (RB_UNLIKELY(cnt > LONG_MAX / sizeof(VALUE))) {
+ if (RB_UNLIKELY(cnt > LONG_MAX / elsize)) {
ruby_malloc_size_overflow(cnt, elsize);
}
+ cnt *= elsize / sizeof(VALUE);
}
else {
size_t size, max = LONG_MAX - sizeof(VALUE) + 1;
Reconsidered and yours seems the intended.
- Status changed from Open to Closed
Applied in changeset trunk|r58902.
attempt to fix rb_alloc_tmp_buffer2 for ALLOCV_N
This is a confusing function to my arithmetic-challenged mind,
but nobu seems alright with this. Anyways this lets me use
large values of elsize without segfaulting, and "make exam"
passes.
- Backport changed from 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: REQUIRED to 2.2: DONTNEED, 2.3: DONTNEED, 2.4: REQUIRED
- Backport changed from 2.2: DONTNEED, 2.3: DONTNEED, 2.4: REQUIRED to 2.2: DONTNEED, 2.3: DONTNEED, 2.4: DONE
ruby_2_4 r59408 merged revision(s) 58902.
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