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reftable: avoid leaks on realloc error

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When realloc(3) fails, it returns NULL and keeps the original allocation
intact.  REFTABLE_ALLOC_GROW overwrites both the original pointer and
the allocation count variable in that case, simultaneously leaking the
original allocation and misrepresenting the number of storable items.

parse_names() and reftable_buf_add() avoid leaking by restoring the
original pointer value on failure, but all other callers seem to be OK
with losing the old allocation.  Add a new variant of the macro,
REFTABLE_ALLOC_GROW_OR_NULL, which plugs the leak and zeros the
allocation counter.  Use it for those callers.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe
2024-12-28 10:47:05 +01:00
committed by Junio C Hamano
parent 76cf4f61c8
commit 8db127d43f
7 changed files with 61 additions and 16 deletions
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30
t/unit-tests/t-reftable-basics.c
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@ -20,6 +20,11 @@ static int integer_needle_lesseq(size_t i, void *_args)
return args->needle <= args->haystack[i];
}
static void *realloc_stub(void *p UNUSED, size_t size UNUSED)
{
return NULL;
}
int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
{
if_test ("binary search with binsearch works") {
@ -141,5 +146,30 @@ int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
check_int(in, ==, out);
}
if_test ("REFTABLE_ALLOC_GROW_OR_NULL works") {
int *arr = NULL;
size_t alloc = 0, old_alloc;
REFTABLE_ALLOC_GROW_OR_NULL(arr, 1, alloc);
check(arr != NULL);
check_uint(alloc, >=, 1);
arr[0] = 42;
old_alloc = alloc;
REFTABLE_ALLOC_GROW_OR_NULL(arr, old_alloc + 1, alloc);
check(arr != NULL);
check_uint(alloc, >, old_alloc);
arr[alloc - 1] = 42;
old_alloc = alloc;
reftable_set_alloc(malloc, realloc_stub, free);
REFTABLE_ALLOC_GROW_OR_NULL(arr, old_alloc + 1, alloc);
check(arr == NULL);
check_uint(alloc, ==, 0);
reftable_set_alloc(malloc, realloc, free);
reftable_free(arr);
}
return test_done();
}