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malloc: fix large tcache code to check for exact size match

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The tcache is used for allocation only if an exact match is found. In the
large tcache code added in commit cbfd798810, we currently extract a
chunk of size greater than or equal to the size we need, but don't check
strict equality. This patch fixes that behaviour.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>
This commit is contained in:
Dev Jain
2025-10-24 16:52:21 +00:00
committed by Wilco Dijkstra
parent 48e040d568
commit b2b4b46a52
1 changed files with 8 additions and 5 deletions
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13
malloc/malloc.c
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@@ -3268,7 +3268,8 @@ tcache_get (size_t tc_idx)
}
static __always_inline tcache_entry **
tcache_location_large (size_t nb, size_t tc_idx, bool *mangled)
tcache_location_large (size_t nb, size_t tc_idx,
bool *mangled, tcache_entry **demangled_ptr)
{
tcache_entry **tep = &(tcache->entries[tc_idx]);
tcache_entry *te = *tep;
@@ -3280,6 +3281,7 @@ tcache_location_large (size_t nb, size_t tc_idx, bool *mangled)
*mangled = true;
}
*demangled_ptr = te;
return tep;
}
@@ -3288,7 +3290,8 @@ tcache_put_large (mchunkptr chunk, size_t tc_idx)
{
tcache_entry **entry;
bool mangled = false;
entry = tcache_location_large (chunksize (chunk), tc_idx, &mangled);
tcache_entry *te;
entry = tcache_location_large (chunksize (chunk), tc_idx, &mangled, &te);
return tcache_put_n (chunk, tc_idx, entry, mangled);
}
@@ -3298,10 +3301,10 @@ tcache_get_large (size_t tc_idx, size_t nb)
{
tcache_entry **entry;
bool mangled = false;
entry = tcache_location_large (nb, tc_idx, &mangled);
tcache_entry *te;
entry = tcache_location_large (nb, tc_idx, &mangled, &te);
if ((mangled && REVEAL_PTR (*entry) == NULL)
|| (!mangled && *entry == NULL))
if (te == NULL || nb != chunksize (mem2chunk (te)))
return NULL;
return tcache_get_n (tc_idx, entry, mangled);