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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id y21-20020a7bcd95000000b003fbb346279dsm3275702wmj.38.2023.08.18.08.58.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Aug 2023 08:58:48 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Cc: Gerd Hoffmann , Christian Schoenebeck Subject: [PATCH 2/2] audio/jackaudio: Avoid dynamic stack allocation in qjack_process() Date: Fri, 18 Aug 2023 16:58:46 +0100 Message-Id: <20230818155846.1651287-3-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230818155846.1651287-1-peter.maydell@linaro.org> References: <20230818155846.1651287-1-peter.maydell@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::335; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x335.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Avoid a dynamic stack allocation in qjack_process(). Since this function is a JACK process callback, we are not permitted to malloc() here, so we allocate a working buffer in qjack_client_init() instead. The codebase has very few VLAs, and if we can get rid of them all we can make the compiler error on new additions. This is a defensive measure against security bugs where an on-stack dynamic allocation isn't correctly size-checked (e.g. CVE-2021-3527). Signed-off-by: Peter Maydell Reviewed-by: Francisco Iglesias Reviewed-by: Christian Schoenebeck --- This feels like we ought to be able to say "we know there are at most X channels, so allocate an array of size X on the stack", but I couldn't find anything in the audio subsystem from a quick look that set an obvious bound on the number of channels. Is there some straightforward constant MAX_CHANNELS somewhere? --- audio/jackaudio.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/audio/jackaudio.c b/audio/jackaudio.c index 7cb2a49f971..e1eaa3477dc 100644 --- a/audio/jackaudio.c +++ b/audio/jackaudio.c @@ -70,6 +70,9 @@ typedef struct QJackClient { int buffersize; jack_port_t **port; QJackBuffer fifo; + + /* Used as workspace by qjack_process() */ + float **process_buffers; } QJackClient; @@ -267,22 +270,21 @@ static int qjack_process(jack_nframes_t nframes, void *arg) } /* get the buffers for the ports */ - float *buffers[c->nchannels]; for (int i = 0; i < c->nchannels; ++i) { - buffers[i] = jack_port_get_buffer(c->port[i], nframes); + c->process_buffers[i] = jack_port_get_buffer(c->port[i], nframes); } if (c->out) { if (likely(c->enabled)) { - qjack_buffer_read_l(&c->fifo, buffers, nframes); + qjack_buffer_read_l(&c->fifo, c->process_buffers, nframes); } else { for (int i = 0; i < c->nchannels; ++i) { - memset(buffers[i], 0, nframes * sizeof(float)); + memset(c->process_buffers[i], 0, nframes * sizeof(float)); } } } else { if (likely(c->enabled)) { - qjack_buffer_write_l(&c->fifo, buffers, nframes); + qjack_buffer_write_l(&c->fifo, c->process_buffers, nframes); } } @@ -448,6 +450,9 @@ static int qjack_client_init(QJackClient *c) jack_get_client_name(c->client)); } + /* Allocate working buffer for process callback */ + c->process_buffers = g_new(float *, c->nchannels); + jack_set_process_callback(c->client, qjack_process , c); jack_set_port_registration_callback(c->client, qjack_port_registration, c); jack_set_xrun_callback(c->client, qjack_xrun, c); @@ -579,6 +584,7 @@ static void qjack_client_fini_locked(QJackClient *c) qjack_buffer_free(&c->fifo); g_free(c->port); + g_free(c->process_buffers); c->state = QJACK_STATE_DISCONNECTED; /* fallthrough */