Date: Wed, 5 Feb 2020 00:20:26 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r357554 - head/sys/kern Message-ID: <202002050020.0150KQJV028310@repo.freebsd.org>
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Author: mjg Date: Wed Feb 5 00:20:26 2020 New Revision: 357554 URL: https://svnweb.freebsd.org/changeset/base/357554 Log: fd: always nullify *fdp in fget* routines Some consumers depend on the pointer being NULL if an error is returned. The guarantee got broken in r357469. Reported by: https://syzkaller.appspot.com/bug?extid=0c9b05e2b727aae21eef Noted by: markj Modified: head/sys/kern/kern_descrip.c Modified: head/sys/kern/kern_descrip.c ============================================================================== --- head/sys/kern/kern_descrip.c Wed Feb 5 00:13:15 2020 (r357553) +++ head/sys/kern/kern_descrip.c Wed Feb 5 00:20:26 2020 (r357554) @@ -2651,6 +2651,7 @@ fget_cap(struct thread *td, int fd, cap_rights_t *need struct file *fp; seqc_t seq; + *fpp = NULL; for (;;) { error = fget_unlocked_seq(fdp, fd, needrightsp, &fp, &seq); if (error != 0) @@ -2905,26 +2906,29 @@ fget_mmap(struct thread *td, int fd, cap_rights_t *rig error = _fget(td, fd, fpp, 0, rightsp); if (maxprotp != NULL) *maxprotp = VM_PROT_ALL; + return (error); #else cap_rights_t fdrights; struct filedesc *fdp; + struct file *fp; seqc_t seq; + *fpp = NULL; fdp = td->td_proc->p_fd; MPASS(cap_rights_is_set(rightsp, CAP_MMAP)); for (;;) { - error = fget_unlocked_seq(fdp, fd, rightsp, fpp, &seq); + error = fget_unlocked_seq(fdp, fd, rightsp, &fp, &seq); if (__predict_false(error != 0)) return (error); - if (__predict_false((*fpp)->f_ops == &badfileops)) { - fdrop(*fpp, td); + if (__predict_false(fp->f_ops == &badfileops)) { + fdrop(fp, td); return (EBADF); } if (maxprotp != NULL) fdrights = *cap_rights(fdp, fd); if (!fd_modified(fdp, fd, seq)) break; - fdrop(*fpp, td); + fdrop(fp, td); } /* @@ -2932,8 +2936,9 @@ fget_mmap(struct thread *td, int fd, cap_rights_t *rig */ if (maxprotp != NULL) *maxprotp = cap_rights_to_vmprot(&fdrights); + *fpp = fp; + return (0); #endif - return (error); } int @@ -2958,24 +2963,27 @@ fget_fcntl(struct thread *td, int fd, cap_rights_t *ri #ifndef CAPABILITIES return (fget_unlocked(fdp, fd, rightsp, fpp)); #else + struct file *fp; int error; seqc_t seq; + *fpp = NULL; MPASS(cap_rights_is_set(rightsp, CAP_FCNTL)); for (;;) { - error = fget_unlocked_seq(fdp, fd, rightsp, fpp, &seq); + error = fget_unlocked_seq(fdp, fd, rightsp, &fp, &seq); if (error != 0) return (error); error = cap_fcntl_check(fdp, fd, needfcntl); if (!fd_modified(fdp, fd, seq)) break; - fdrop(*fpp, td); + fdrop(fp, td); } if (error != 0) { - fdrop(*fpp, td); - *fpp = NULL; + fdrop(fp, td); + return (error); } - return (error); + *fpp = fp; + return (0); #endif }
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