- Handle negative second values properly when converting a timespec64 to nanoseconds.
time: Handle negative seconds correctly in timespec64_to_ns()

timespec64_ns() prevents multiplication overflows by comparing the seconds
value of the timespec to KTIME_SEC_MAX. If the value is greater or equal it
returns KTIME_MAX.

But that check casts the signed seconds value to unsigned which makes the
comparision true for all negative values and therefore return wrongly

Negative second values are perfectly valid and required in some places,
e.g. ptp_clock_adjtime().

Remove the cast and add a check for the negative boundary which is required
to prevent undefined behaviour due to multiplication underflow.

Fixes: cb47755725da ("time: Prevent undefined behaviour in timespec64_to_ns()")'
Signed-off-by: Lukas Hannen <lukas.hannen@opensource.tttech-industrial.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/AM6PR01MB541637BD6F336B8FFB72AF80EEC69@AM6PR01MB5416.eurprd01.prod.exchangelabs.com
1 file changed