Re: [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery

Borislav Petkov
2021-08-22T14:45:38Z

On Fri, Aug 20, 2021 at 01:33:56PM -0700, Luck, Tony wrote:
> The new version (thanks to All fixing iov_iter.c) now does
> exactly what POSIX says should happen. If I have a buffer
> with poison at offset 213, and I do this:
>
> ret = write(fd, buf, 512);
>
> Then the return from write is 213, and the first 213 bytes
> from the buffer appear in the file, and the file size is
> incremented by 213 (assuming the write started with the lseek
> offset at the original size of the file).

... and the user still gets a SIGBUS so that it gets a chance to handle
the encountered poison? I.e., not retry the write for the remaining 512
- 213 bytes?

If so, do we document that somewhere so that application writers can
know what they should do in such cases?

--
Regards/Gruss,
Boris.