Messages in this thread | | | Date | Wed, 28 Apr 2010 17:39:33 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 3/3] RFC: p9auth: add p9auth fs |
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On 04/28, Serge E. Hallyn wrote: > > Quoting Oleg Nesterov (oleg@redhat.com): > > > > +static ssize_t p9auth_use_write(struct file *file, const char __user *buffer, > > > + size_t count, loff_t *ppos) > > > +{ > > > + ssize_t retval = -ENOMEM; > > > + char *user_buf; > > > + > > > + if (mutex_lock_interruptible(&cap_mutex)) > > > + return -EINTR; > > > > EINTR doesn't look exactly right here, especially if TIF_SIGPENDING is > > spurious. Probably ERESTARTNOINTR makes more sense. Or mutex_lock_killable(). > > Ashwin had had this as ERESTARTSYS I believe. I'd read something about > userspace should only see -EINTR so I changed it.
Yes, ERESTARTxxx should not be visible to the user-space. But it is OK to return it from the syscall if signal_pending() is true, in this case it will be changed to EINTR or the system call will be restarted.
ERESTARTNOINTR always restarts the syscall, perphaps after handling the signal if it is really pending.
> > > + if (copy_from_user(user_buf, buffer, count)) { > > > + retval = -EFAULT; > > > + goto out; > > > + } > > > + > > > + retval = use_setuid_capability(user_buf); > > > > It seems that use_setuid_capability() pathes assume that user_buf is > > null terminated? Say, parse_user_capability() does kstrdup(user_buf). > > I kzalloc()d to count+1 before, and only copy_from_user() count bytes, > so the last byte should always be 0.
Ah, indeed, thanks.
Oleg.
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