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Wed, 5 Aug 2026 21:11:16 -0400 (EDT) From: Junio C Hamano To: "Johannes Schindelin via GitGitGadget" Cc: git@vger.kernel.org, Patrick Steinhardt , Johannes Schindelin Subject: Re: [PATCH v2 03/11] reftable/block: check deflateInit() return value In-Reply-To: <9bf7e737c740d8a80467ee3b38df9c86bbf7a566.1785954661.git.gitgitgadget@gmail.com> (Johannes Schindelin via GitGitGadget's message of "Wed, 05 Aug 2026 18:30:52 +0000") References: <9bf7e737c740d8a80467ee3b38df9c86bbf7a566.1785954661.git.gitgitgadget@gmail.com> Date: Wed, 05 Aug 2026 18:11:15 -0700 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain "Johannes Schindelin via GitGitGadget" writes: > The function already uses REFTABLE_ZLIB_ERROR for deflate() > failures later in the code path (lines 171, 199), so returning > the same error code for deflateInit() failure is consistent. > > Pointed out by Coverity. > > Assisted-by: Claude Opus 4.6 > Signed-off-by: Johannes Schindelin > --- > reftable/block.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/reftable/block.c b/reftable/block.c > index 920b3f4486..ec81fd0493 100644 > --- a/reftable/block.c > +++ b/reftable/block.c > @@ -87,7 +87,8 @@ int block_writer_init(struct block_writer *bw, uint8_t typ, uint8_t *block, > REFTABLE_CALLOC_ARRAY(bw->zstream, 1); > if (!bw->zstream) > return REFTABLE_OUT_OF_MEMORY_ERROR; > - deflateInit(bw->zstream, 9); > + if (deflateInit(bw->zstream, 9) != Z_OK) > + return REFTABLE_ZLIB_ERROR; > } Presumably bw->zstream occupies some memory allocated on the heap. Does a failing deflateInit() release it? If not, do we leak memory here? Or do we need if (deflateInit(bw->zstream, 9) !+ Z_OK) { REFTABLE_FREE_AND_NULL(bw->zstream); return REFTABLE_ZLIB_ERROR; } here? Noticing and returning an error is a good first step. The only caller of it is reftable/writer.c:writer_reinit_block_writer(), and it checks and relays the error code from here to its callers, but not all callers of it check the error condition. The most blatant offender being reftable_writer_new() that happily keeps going. I do not know if we end up calling zlib on bw->zstream for such a broken block_writer(), as I didn't trace the call graph fully myself. Stepping back a bit, if REFTABLE_CALLOC_ARRAY() fails, bw->zstream would be NULL, and a caller that does not check the return value of writer_reinit_block_writer() would be holding a block writer whose zstream is NULL. If the block writer is eventually passed to the block_writer_release() function, we would call deflateEnd() on it.