In the Linux kernel, the following vulnerability has been resolved: rtc: mpfs: fix unchecked devm_clk_get() error pointer in probe() devm_

In the Linux kernel, the following vulnerability has been resolved:

rtc: mpfs: fix unchecked devm_clk_get() error pointer in probe()

devm_clk_get(&pdev->dev, "rtcref")'s return value was passed straight
into clk_get_rate() without checking it for an error first, unlike the
"rtc" clock a few lines above which is correctly checked with
IS_ERR(). clk_get_rate() only guards against a NULL clk, not an error
pointer:

 1if (!clk)
 2	return 0;
 3...
 4rate = clk_core_get_rate_recalc(clk->core);

so if devm_clk_get() ever returns an error pointer here (for example
ERR_PTR(-EPROBE_DEFER), which is the normal, expected outcome if the
clkcfg clock-provider this RTC depends on has not registered its
clocks yet by the time this driver probes), clk_get_rate() dereferences
that error pointer instead of returning 0, crashing instead of letting
probe defer.

Capture the clock in the existing 'clk' local and check it with
IS_ERR() before calling clk_get_rate(), matching the handling already
used for the "rtc" clock in this same function.