On Sun 2020-12-06 21:57:46, John Ogness wrote: > On 2020-12-04, Petr Mladek <[email protected]> wrote: > >> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > >> index e9018c4e1b66..7385101210be 100644 > >> --- a/kernel/printk/printk.c > >> +++ b/kernel/printk/printk.c > >> @@ -785,7 +749,6 @@ static loff_t devkmsg_llseek(struct file *file, loff_t > >> offset, int whence) > >> if (offset) > >> return -ESPIPE; > >> > >> - logbuf_lock_irq(); > > > > user->seq manipulation is not longer safe from the atomicity point of > > view. > > > > One solution would be to use atomic variable in struct devkmsg_user(). > > Another solution would be to synchronize it with user->lock like we do > > in devkmsg_read(). > > > > user->lock looks like an overhead. But it actually would make sense to > > prevent seek in the middle of a read. > > I would prefer using atomic64_t. Using user->lock could introduce some > wacky regression.
OK, fair enough. User space might do crazy stuff. Best Regards, Petr
