Date: Tue, 22 Dec 2015 09:26:24 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r292592 - head/sys/fs/cuse Message-ID: <201512220926.tBM9QOq3044469@repo.freebsd.org>
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Author: hselasky Date: Tue Dec 22 09:26:24 2015 New Revision: 292592 URL: https://svnweb.freebsd.org/changeset/base/292592 Log: Guard against the same process being both CUSE server and client at the same time. This can easily lead to a deadlock when destroying the character devices nodes. Modified: head/sys/fs/cuse/cuse.c Modified: head/sys/fs/cuse/cuse.c ============================================================================== --- head/sys/fs/cuse/cuse.c Tue Dec 22 09:08:21 2015 (r292591) +++ head/sys/fs/cuse/cuse.c Tue Dec 22 09:26:24 2015 (r292592) @@ -108,6 +108,7 @@ struct cuse_server { TAILQ_HEAD(, cuse_client) hcli; struct cv cv; struct selinfo selinfo; + pid_t pid; int is_closing; int refs; }; @@ -691,6 +692,10 @@ cuse_server_open(struct cdev *dev, int f free(pcs, M_CUSE); return (ENOMEM); } + + /* store current process ID */ + pcs->pid = curproc->p_pid; + TAILQ_INIT(&pcs->head); TAILQ_INIT(&pcs->hdev); TAILQ_INIT(&pcs->hcli); @@ -1357,9 +1362,15 @@ cuse_client_open(struct cdev *dev, int f if (pcsd != NULL) { pcs = pcsd->server; pcd = pcsd->user_dev; + /* + * Check that the refcount didn't wrap and that the + * same process is not both client and server. This + * can easily lead to deadlocks when destroying the + * CUSE character device nodes: + */ pcs->refs++; - if (pcs->refs < 0) { - /* overflow */ + if (pcs->refs < 0 || pcs->pid == curproc->p_pid) { + /* overflow or wrong PID */ pcs->refs--; pcsd = NULL; }
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