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soundwire: fix double free of dangling pointer 

[ Upstream commit 3fbbf2148a ]

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: 99b8a5d608 ("soundwire: Add bank switch routine")
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200902202650.14189-1-trix@redhat.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Tom Rix 2020-09-02 13:26:50 -07:00 committed by Greg Kroah-Hartman
parent 122cdbd501
commit fe0278843b
1 changed files with 5 additions and 3 deletions
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8
drivers/soundwire/stream.c
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@ -702,6 +702,7 @@ error:
kfree(wbuf);
error_1:
kfree(wr_msg);
bus->defer_msg.msg = NULL;
return ret;
}
@ -825,9 +826,10 @@ 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: