[Git][wine/wine][master] ntdll: Fix inconsistency in LFH block size calculation during realloc.

[Alexandre Julliard (＠julliard)]

Alexandre Julliard pushed to branch master at wine / wine

Commits:
dd22c706 by Yuxuan Shui at 2025-07-30T23:09:41+09:00
ntdll: Fix inconsistency in LFH block size calculation during realloc.

For allocation, the block size calculation is snapped to block bin sizes, but
for reallocation it is not. So the tail_size calculation will be wrong if the
block size is not one of the bin sizes.

To illustrate the problem: assume an allocation size of 32 bytes.
heap_get_block_size will return 40 bytes. heap_allocate_block_lfh will round
it up to 48 bytes. The tail_size is thus, 48 - 8 - 32 = 8 bytes. Later,
HeapReAlloc is called to shrink it to 30 bytes. heap_get_block_size returns
40 bytes, heap_resize_block_lfh will not return STATUS_NO_MEMORY, because
ROUND_SIZE(30) == 32, and 30 < 32. It will then calculate the tail_size based
on the new block_size, which is 40 bytes. So the new tail_size becomes:
40 - 8 - 30 = 2 bytes. But block->block_size is still 48 bytes! So what it
actually did is **growing** the block to 48 - 8 - 2 = 38 bytes from 32 bytes.

This commit fixes it by also rounding up the block_size to bin sizes in
heap_resize_block_lfh.

- - - - -

1 changed file:

- dlls/ntdll/heap.c

View it on GitLab: https://gitlab.winehq.org/wine/wine/-/commit/dd22c706cc31b10f3db4e9929a09cbd...