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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id i73sm330622ill.4.2020.09.02.13.26.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Sep 2020 13:26:55 -0700 (PDT) From: trix@redhat.com To: vkoul@kernel.org, yung-chuan.liao@linux.intel.com, pierre-louis.bossart@linux.intel.com, sanyog.r.kale@intel.com, natechancellor@gmail.com, ndesaulniers@google.com, shreyas.nc@intel.com Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Tom Rix Subject: [PATCH v2] soundwire: fix double free of dangling pointer Date: Wed, 2 Sep 2020 13:26:50 -0700 Message-Id: <20200902202650.14189-1-trix@redhat.com> X-Mailer: git-send-email 2.18.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tom Rix clang static analysis flags this problem stream.c:844:9: warning: Use of memory after it is freed kfree(bus->defer_msg.msg->buf); ^~~~~~~~~~~~~~~~~~~~~~~ This happens in an error handler cleaning up memory allocated for elements in a list. list_for_each_entry(m_rt, &stream->master_list, stream_node) { bus = m_rt->bus; kfree(bus->defer_msg.msg->buf); kfree(bus->defer_msg.msg); } And is triggered when the call to sdw_bank_switch() fails. There are a two problems. First, when sdw_bank_switch() fails, though it frees memory it does not clear bus's reference 'defer_msg.msg' to that memory. The second problem is the freeing msg->buf. In some cases msg will be NULL so this will dereference a null pointer. Need to check before freeing. Fixes: 99b8a5d608a6 ("soundwire: Add bank switch routine") Signed-off-by: Tom Rix Reviewed-by: Nick Desaulniers Reviewed-by: Pierre-Louis Bossart --- v2 : change title, was 'soundwire: fix error handling' --- drivers/soundwire/stream.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index 37290a799023..6e36deb505b1 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -717,6 +717,7 @@ static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count) kfree(wbuf); error_1: kfree(wr_msg); + bus->defer_msg.msg = NULL; return ret; } @@ -840,9 +841,10 @@ static int do_bank_switch(struct sdw_stream_runtime *stream) error: list_for_each_entry(m_rt, &stream->master_list, stream_node) { bus = m_rt->bus; - - kfree(bus->defer_msg.msg->buf); - kfree(bus->defer_msg.msg); + if (bus->defer_msg.msg) { + kfree(bus->defer_msg.msg->buf); + kfree(bus->defer_msg.msg); + } } msg_unlock: -- 2.18.1