On Wed, 10 Sep 2025 16:18:20 -0400 Steven Rostedt <[email protected]> wrote:
> From: Steven Rostedt <[email protected]> > > The functions __copy_from_user_inatomic() and __copy_to_user_inatomic() > both require that either the user space memory is pinned, or that page > faults are disabled when they are called. If page faults are not disabled, > and the memory is not present, the fault handling of reading or writing to > that memory may cause the kernel to schedule. That would be bad in an > atomic context. > > Link: > https://lore.kernel.org/all/[email protected]/ > Looks good to me. Reviewed-by: Masami Hiramatsu (Google) <[email protected]> Thanks, > Signed-off-by: Steven Rostedt (Google) <[email protected]> > --- > include/linux/uaccess.h | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index 1beb5b395d81..add99fa9b656 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -86,6 +86,12 @@ > * as usual) and both source and destination can trigger faults. > */ > > +/* > + * __copy_from_user_inatomic() is safe to use in an atomic context but > + * the user space memory must either be pinned in memory, or page faults > + * must be disabled, otherwise the page fault handling may cause the function > + * to schedule. > + */ > static __always_inline __must_check unsigned long > __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) > { > @@ -124,7 +130,8 @@ __copy_from_user(void *to, const void __user *from, > unsigned long n) > * Copy data from kernel space to user space. Caller must check > * the specified block with access_ok() before calling this function. > * The caller should also make sure he pins the user space address > - * so that we don't result in page fault and sleep. > + * or call page_fault_disable() so that we don't result in a page fault > + * and sleep. > */ > static __always_inline __must_check unsigned long > __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) > -- > 2.50.1 > > -- Masami Hiramatsu (Google) <[email protected]>
