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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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10
reftable/block.c
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@ -53,7 +53,8 @@ static int block_writer_register_restart(struct block_writer *w, int n,
if (2 + 3 * rlen + n > w->block_size - w->next)
return -1;
if (is_restart) {
REFTABLE_ALLOC_GROW(w->restarts, w->restart_len + 1, w->restart_cap);
REFTABLE_ALLOC_GROW_OR_NULL(w->restarts, w->restart_len + 1,
w->restart_cap);
if (!w->restarts)
return REFTABLE_OUT_OF_MEMORY_ERROR;
w->restarts[w->restart_len++] = w->next;
@ -176,7 +177,8 @@ int block_writer_finish(struct block_writer *w)
* is guaranteed to return `Z_STREAM_END`.
*/
compressed_len = deflateBound(w->zstream, src_len);
REFTABLE_ALLOC_GROW(w->compressed, compressed_len, w->compressed_cap);
REFTABLE_ALLOC_GROW_OR_NULL(w->compressed, compressed_len,
w->compressed_cap);
if (!w->compressed) {
ret = REFTABLE_OUT_OF_MEMORY_ERROR;
return ret;
@ -235,8 +237,8 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block,
uLong src_len = block->len - block_header_skip;
/* Log blocks specify the *uncompressed* size in their header. */
REFTABLE_ALLOC_GROW(br->uncompressed_data, sz,
br->uncompressed_cap);
REFTABLE_ALLOC_GROW_OR_NULL(br->uncompressed_data, sz,
br->uncompressed_cap);
if (!br->uncompressed_data) {
err = REFTABLE_OUT_OF_MEMORY_ERROR;
goto done;