time: Handle negative seconds correctly in timespec64_to_ns()
commit 39ff83f2f6cc5cc1458dfcea9697f96338210beb upstream.
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
KTIME_MAX.
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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/AM6PR01MB541637BD6F336B8FFB72AF80EEC69@AM6PR01MB5416.eurprd01.prod.exchangelabs.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>
1 file changed
