• Martin Blumenstingl's avatar
    clk: Fix potential NULL dereference in clk_fetch_parent_index() · 96ece579
    Martin Blumenstingl authored
    [ Upstream commit 24876f09 ]
    
    Don't compare the parent clock name with a NULL name in the
    clk_parent_map. This prevents a kernel crash when passing NULL
    core->parents[i].name to strcmp().
    
    An example which triggered this is a mux clock with four parents when
    each of them is referenced in the clock driver using
    clk_parent_data.fw_name and then calling clk_set_parent(clk, 3rd_parent)
    on this mux.
    In this case the first parent is also the HW default so
    core->parents[i].hw is populated when the clock is registered. Calling
    clk_set_parent(clk, 3rd_parent) will then go through all parents and
    skip the first parent because it's hw pointer doesn't match. For the
    second parent no hw pointer is cached yet and clk_core_get(core, 1)
    returns a non-matching pointer (which is correct because we are comparing
    the second with the third parent). Comparing the result of
    clk_core_get(core, 2) with the requested parent gives a match. However
    we don't reach this point because right after the clk_core_get(core, 1)
    mismatch the old code tried to !strcmp(parent->name, NULL) (where the
    second argument is actually core->parents[i].name, but that was never
    populated by the clock driver).
    Signed-off-by: default avatarMartin Blumenstingl <[email protected]>
    Link: https://lkml.kernel.org/r/[email protected]
    Fixes: fc0c209c ("clk: Allow parents to be specified without string names")
    Signed-off-by: default avatarStephen Boyd <[email protected]>
    Signed-off-by: default avatarSasha Levin <[email protected]>
    96ece579
clk.c 115 KB