On (07/14/17 14:51), Petr Mladek wrote: > printk_late_init() is responsible for disabling boot consoles that > use init memory. It checks the address of struct console for this. > > But this is not enough. For example, there are several early > consoles that have write() method in the init section and > struct console in the normal section. They are not disabled > and could cause fancy and hard to debug system states. > > It is even more complicated by the macros EARLYCON_DECLARE() and > OF_EARLYCON_DECLARE() where various struct members are set at > runtime by the provided setup() function. > > I have tried to reproduce this problem and forced the classic uart > early console to stay using keep_bootcon parameter. In particular > I used earlycon=uart,io,0x3f8 keep_bootcon console=ttyS0,115200. > The system did not boot: > > [ 1.570496] PM: Image not found (code -22) > [ 1.570496] PM: Image not found (code -22) > [ 1.571886] PM: Hibernation image not present or could not be loaded. > [ 1.571886] PM: Hibernation image not present or could not be loaded. > [ 1.576407] Freeing unused kernel memory: 2528K > [ 1.577244] kernel tried to execute NX-protected page - exploit attempt? (uid: 0) > > The double lines are caused by having both early uart console and > ttyS0 console enabled at the same time. The early console stopped > working when the init memory was freed. Fortunately, the invalid > call was caught by the NX-protexted page check and did not cause > any silent fancy problems. > > This patch adds a check for many other addresses stored in > struct console. It omits setup() and match() that are used > only when the console is registered. Therefore they have > already been used at this point and there is no reason > to use them again. > > Signed-off-by: Petr Mladek <pmladek@xxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> -ss -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
