On Wed 2018-02-28 12:42:24, Andy Shevchenko wrote: > On Wed, 2018-02-28 at 11:04 +0100, Petr Mladek wrote: > > On Tue 2018-02-27 19:35:50, Andy Shevchenko wrote: > > > On Tue, 2018-02-27 at 16:50 +0100, Petr Mladek wrote: > > Note that it will most likely crash in vprintk_emit() on the line > > > > text_len = vscnprintf(text, sizeof(textbuf), fmt, args); > > > > It will be with logbug_lock() taken. The nested printk() messages > > will be stored in per-CPU buffer thanks to printk_safe code. > > Yeah, that's bad. > > > IMHO, it would make sense to hanve this check also pointers that are > > being deferred. > > Send a patch to discuss!
I thought about this more. IMHO, the check for PAGE_SIZE in pointer() makes perfect sense. It helps to avoid crash and actually see the message. I am going to send the patch in a minute. BTW: I am not sure who is going to pass this patchset to Linus. If nobody is against, I could eventually do so via printk.git. > > > > To be honest, I do not feel experienced enough to decide > > > > about the preferred behavior. On one hand, it is bad when > > > > printk() would crash the kernel. On the other hand, hiding wide > > > > range of values under "(null)" string might confuse people. > > > > Would it make sense to survive and write different strings for > > > > difference intervals? For example? > > > > > > > > "(null)" for ptr == 0 > > > > "(null-16)" for ptr > 0 && ptr <= 16 > > > > "(null-pg)" for prt > 16 && ptr <= PAGE_SIZE > > > > > > > > In each case, this patch changes the behavior and it should > > > > be documented in the commit message. > > > > > > Personally I strongly disagree with blowing code up in such places > > > for little or none benefit. > > Send a patch to discuss! I am not going to do so unless there is an evidence that people are confused or that the above idea is desired. Best Regards, Petr