On 20120705-00:09, Linus Walleij wrote:
> The clk_change_rate() code would dereference clk->parent
> to get clk->parent->rate without first checking that clk->parent
> was valid. This doesn't work if the clock is (A) a root clock
> and (B) can change rate. Such is the case with a VCO clock
> like the ICST which consequently crash like this without
> this patch:
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000001c
> pgd = c0004000
> [0000001c] *pgd=00000000
> Internal error: Oops: 5 [#1] PREEMPT ARM
> Modules linked in:
> CPU: 0 Not tainted (3.5.0-rc3-00003-g8156866-dirty #193)
> PC is at clk_change_rate+0x34/0xd8
> LR is at clk_change_rate+0x18/0xd8
>
> Cc: [email protected]
> Cc: Mike Turquette <[email protected]>
> Cc: Ulf Hansson <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
Hi Linus,
This has been fixed in Pawell's patch, "clk: Check parent for NULL in
clk_change_rate".
Thanks,
Mike
> ---
> drivers/clk/clk.c | 22 +++++++++++++++-------
> 1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 687b00d..032d79c 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -854,14 +854,22 @@ static void clk_change_rate(struct clk *clk)
>
> old_rate = clk->rate;
>
> - if (clk->ops->set_rate)
> - clk->ops->set_rate(clk->hw, clk->new_rate, clk->parent->rate);
> + if (clk->ops->set_rate) {
> + if (clk->parent)
> + clk->ops->set_rate(clk->hw, clk->new_rate,
> + clk->parent->rate);
> + else
> + clk->ops->set_rate(clk->hw, clk->new_rate, 0);
> + }
>
> - if (clk->ops->recalc_rate)
> - clk->rate = clk->ops->recalc_rate(clk->hw,
> - clk->parent->rate);
> - else
> - clk->rate = clk->parent->rate;
> + if (clk->ops->recalc_rate) {
> + if (clk->parent)
> + clk->rate = clk->ops->recalc_rate(clk->hw,
> + clk->parent->rate);
> + else
> + clk->rate = clk->ops->recalc_rate(clk->hw, 0);
> + } else
> + clk->rate = clk->parent ? clk->parent->rate : 0;
>
> if (clk->notifier_count && old_rate != clk->rate)
> __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);
> --
> 1.7.10.4
>
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