Date: Fri, 4 Dec 2020 02:20:42 +0000 (UTC) From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r368323 - stable/12/sys/kern Message-ID: <202012040220.0B42KgET055959@repo.freebsd.org>
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Author: kevans Date: Fri Dec 4 02:20:41 2020 New Revision: 368323 URL: https://svnweb.freebsd.org/changeset/base/368323 Log: MFC r368006: kern: never restart syscalls calling closefp(), e.g. close(2) All paths leading into closefp() will either replace or remove the fd from the filedesc table, and closefp() will call fo_close methods that can and do currently sleep without regard for the possibility of an ERESTART. This can be dangerous in multithreaded applications as another thread could have opened another file in its place that is subsequently operated on upon restart. The following are seemingly the only ones that will pass back ERESTART in-tree: - sockets (SO_LINGER) - fusefs - nfsclient Modified: stable/12/sys/kern/kern_descrip.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/kern_descrip.c ============================================================================== --- stable/12/sys/kern/kern_descrip.c Fri Dec 4 02:19:45 2020 (r368322) +++ stable/12/sys/kern/kern_descrip.c Fri Dec 4 02:20:41 2020 (r368323) @@ -1223,6 +1223,15 @@ closefp(struct filedesc *fdp, int fd, struct file *fp, FILEDESC_XUNLOCK(fdp); error = closef(fp, td); + + /* + * All paths leading up to closefp() will have already removed or + * replaced the fd in the filedesc table, so a restart would not + * operate on the same file. + */ + if (error == ERESTART) + error = EINTR; + if (holdleaders) { FILEDESC_XLOCK(fdp); fdp->fd_holdleaderscount--;
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