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reftable/merged: fix zero-sized allocation when there are no readers

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It was reported [1] that Git started to fail with an out-of-memory error
when initializing repositories with the reftable backend on NonStop
platforms. A bisect led to 802c0646ac (reftable/merged: handle
allocation failures in `merged_table_init_iter()`, 2024-10-02), which
changed how we allocate memory when initializing a merged table.

The root cause of this seems to be that NonStop returns a `NULL` pointer
when doing a zero-sized allocation. This would've already happened
before the above change, but we never noticed because we did not check
the result. Now we do notice and thus return an out-of-memory error to
the caller.

Fix the issue by skipping the allocation altogether in case there are no
readers.

[1]: <00ad01db5017$aa9ce340$ffd6a9c0$@nexbridge.com>

Reported-by: Randall S. Becker <rsbecker@nexbridge.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Patrick Steinhardt
2024-12-22 08:24:29 +01:00
committed by Junio C Hamano
parent 8e27ee9220
commit 5ab83521cf
1 changed files with 7 additions and 5 deletions
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12
reftable/merged.c
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@ -238,14 +238,16 @@ int merged_table_init_iter(struct reftable_merged_table *mt,
struct reftable_iterator *it,
uint8_t typ)
{
struct merged_subiter *subiters;
struct merged_subiter *subiters = NULL;
struct merged_iter *mi = NULL;
int ret;
REFTABLE_CALLOC_ARRAY(subiters, mt->readers_len);
if (!subiters) {
ret = REFTABLE_OUT_OF_MEMORY_ERROR;
goto out;
if (mt->readers_len) {
REFTABLE_CALLOC_ARRAY(subiters, mt->readers_len);
if (!subiters) {
ret = REFTABLE_OUT_OF_MEMORY_ERROR;
goto out;
}
}
for (size_t i = 0; i < mt->readers_len; i++) {