Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 25 Nov 2019 19:39:34 -0800 | Subject | Re: Commit 0be0ee71 ("fs: properly and reliably lock f_pos in fdget_pos()") breaking userspace |
| |
On Mon, Nov 25, 2019 at 7:21 PM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > Of course, this may fix the f_pos locking issue, but replace it with a > "oops, the character device driver tried to look at *pos anyway", and > that will give you a nice OOPS instead.
Confirmed. At least the x86 firmware update code uses "simple_read_from_buffer()", which does use the file position, but doesn't actually allow llseek().
So no, "it's a character device no llseek" does not mean that it acts as a pure streaming device with no file position, and we'd actually have to mark individual drivers (either by adding 'stream_open()' in their open routines, or adding the extra field to 'struct file_operations' that I mentioned).
I think I'll have to revert that trial commit. I'll give it another day in case somebody has a better idea, but it looks like it's too early to do that nice cleanup as things are now.
Linus
| |