On 8/31/20 12:47 PM, Nick Desaulniers wrote:
On Sat, Aug 29, 2020 at 8:35 AM <trix@xxxxxxxxxx> wrote:From: Tom Rix <trix@xxxxxxxxxx> 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 <trix@xxxxxxxxxx> --- 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;This fix looks correct to me because L668 sets `bus->defer_msg.msg = wr_msg;`, but on error L719 frees `wr_msg`, so now `bus->defer_msg.msg` is a dangling pointer.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); + }I'd prefer a conditional check for each, but sdw_ml_sync_bank_switch() has this same pattern, so it looks like the lifetime of these two match. Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Also looks good to me. Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
