On (07/14/17 14:51), Petr Mladek wrote: > From: Matt Redfearn <[email protected]> > > Commit 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in > printk_late_init() if keep_bootcon") added a check on keep_bootcon to > ensure that boot consoles were kept around until the real console is > registered. > > This can lead to problems if the boot console data and code are in the > init section, since it can be freed before the boot console is > unregistered. > > Commit 81cc26f2bd11 ("printk: only unregister boot consoles when > necessary") fixed this a better way. It allowed to keep boot consoles > that did not use init data. Unfortunately it did not remove the check > of keep_bootcon. > > This can lead to crashes and weird panics when the bootconsole is > accessed after free, especially if page poisoning is in use and the > code / data have been overwritten with a poison value. > > To prevent this, always free the boot console if it is within the init > section. In addition, print a warning about that the console is removed > prematurely. > > Finally there is a new comment how to avoid the warning. It replaced > an explanation that duplicated a more comprehensive function > description few lines above. > > Fixes: 4c30c6f566c0 ("kernel/printk: do not turn off bootconsole in > printk_late_init() if keep_bootcon") > Signed-off-by: Matt Redfearn <[email protected]> > [[email protected]: print the warning, code and comments clean up] > Signed-off-by: Petr Mladek <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]> -ss
