On 2021-01-14, Petr Mladek <[email protected]> wrote: > It is pitty that I have missed this. I remember that I discussed > exactly this problem before, see > https://lore.kernel.org/lkml/[email protected]/ > > And I did exactly the same mistake. I have missed the two users in > "arch/powerpc" and "arch/um". > > It is clear that this problem happens repeatedly.
Yes, because the semantics are poor and undocumented. > Now, the change in record_printk_text() behavior affects also other > callers. For example, syslog_print() fills the buffer completely > as well now. I could imagine a userspace code that does the same > mistake and it works just by chance. No, syslog_print() works fine. There are only 2 users that think they can blindly add a byte at buffer[len]. Their code looks scary just seeing it. > We should restore the original record_printk_text() behavior > and add the comment explaining why it is done this way. OK. > And I would even explicitly add the trailing '\0' as suggested at > https://lore.kernel.org/lkml/[email protected]/#t OK. But then this becomes official semantics so powerpc/um no longer need to append a terminator. John Ogness
