Date: Thu, 29 Oct 2015 13:53:37 +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: r290140 - head/sys/kern Message-ID: <201510291353.t9TDrbvD013568@repo.freebsd.org>
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Author: hselasky Date: Thu Oct 29 13:53:37 2015 New Revision: 290140 URL: https://svnweb.freebsd.org/changeset/base/290140 Log: Add missing NULL check in physio(). When destroying a character device the si_devsw field is set to NULL before all references are gone, to indicate the character device is going away. This can cause a NULL-dereference fault inside physio(). The callers of physio() should own a thread reference on the cdev and if si_devsw is seen as non-NULL, it is usable during the execution of the function. Else an ENXIO error code is returned. Reviewed by: kib MFC after: 2 weeks Modified: head/sys/kern/kern_physio.c Modified: head/sys/kern/kern_physio.c ============================================================================== --- head/sys/kern/kern_physio.c Thu Oct 29 10:31:44 2015 (r290139) +++ head/sys/kern/kern_physio.c Thu Oct 29 13:53:37 2015 (r290140) @@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$"); int physio(struct cdev *dev, struct uio *uio, int ioflag) { + struct cdevsw *csw; struct buf *pbuf; struct bio *bp; struct vm_page **pages; @@ -46,6 +47,11 @@ physio(struct cdev *dev, struct uio *uio int error, i, npages, maxpages; vm_prot_t prot; + csw = dev->si_devsw; + /* check if character device is being destroyed */ + if (csw == NULL) + return (ENXIO); + /* XXX: sanity check */ if(dev->si_iosize_max < PAGE_SIZE) { printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n", @@ -165,7 +171,7 @@ physio(struct cdev *dev, struct uio *uio } } - dev->si_devsw->d_strategy(bp); + csw->d_strategy(bp); if (uio->uio_rw == UIO_READ) biowait(bp, "physrd"); else
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