Excerpts from Thadeu Lima de Souza Cascardo's message of August 7, 2020 1:36 pm: > On Fri, Aug 07, 2020 at 08:48:46AM -0700, Linus Torvalds wrote: >> On Fri, Aug 7, 2020 at 8:19 AM Alex Xu (Hello71) <[email protected]> wrote: >> > >> > On Linus' master, wine fails to start with the following error: >> > >> > wine client error:0: write: Bad file descriptor >> > >> > This issue is not present on 5.8. It appears to be caused by failure to >> > write to a pipe FD received via SCM_RIGHTS. Therefore, I tried reverting >> > 9ecc6ea491f0, which resolved the issue. >> >> Would you mind trying to bisect exactly where it happens? >> > > This report [1] seemed related and pointed out at c0029de50982 ("net/scm: > Regularize compat handling of scm_detach_fds()"). The use of CMSG_USER_DATA > instead of CMSG_COMPAT_DATA seems fishy. > > Alex, can you try applying the patch below? > > Cascardo. > > [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-August/216156.html > >> I don't think any of the commits in that pull are supposed to change >> semantics, and while reverting the whole merge shows that yes, that's >> what brought in the problems, it would be good to pinpoint just which >> change breaks so that we can fix just that thing. >> >> Kees, ideas? >> >> Linus > > --- > diff --git a/net/compat.c b/net/compat.c > index 703acb51c698..95ce707a30a3 100644 > --- a/net/compat.c > +++ b/net/compat.c > @@ -294,7 +294,7 @@ void scm_detach_fds_compat(struct msghdr *msg, struct > scm_cookie *scm) > (struct compat_cmsghdr __user *)msg->msg_control; > unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC > : 0; > int fdmax = min_t(int, scm_max_fds_compat(msg), scm->fp->count); > - int __user *cmsg_data = CMSG_USER_DATA(cm); > + int __user *cmsg_data = CMSG_COMPAT_DATA(cm); > int err = 0, i; > > for (i = 0; i < fdmax; i++) { >
Yes, this seems to work. Tested-by: Alex Xu (Hello71) <[email protected]> Thanks!
