[PATCH] clk: mediatek: mt6779: Fix a NULL pointer dereference in clk_mt6779_top_probe()

[miles.chen at mediatek.com]

Hi Qingyang,

> Fix this bug by adding a check of clk_data.
> 
> Another way to fix this bug is to add a check of clk_data in
> mtk_clk_register_muxes(), which may solve many similar bugs but could
> cause potential problems to previously correct cases as the API is changed.
> 
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
> Builds with CONFIG_COMMON_CLK_MT6779=y show no new warnings,
> and our static analyzer no longer warns about this code.
> 
> Fixes: 710774e04861 ("clk: mediatek: Add MT6779 clock support")
> Signed-off-by: Zhou Qingyang <zhou1615 at umn.edu>
>

thanks,
Reviewed-by: Miles Chen <miles.chen at mediatek.com>