From cb3450e26e6be9ceea1cf9e73995356fd0b923c3 Mon Sep 17 00:00:00 2001 From: Hans Petter Selasky Date: Thu, 29 Oct 2015 13:53:37 +0000 Subject: [PATCH] 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 --- sys/kern/kern_physio.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/sys/kern/kern_physio.c b/sys/kern/kern_physio.c index 71cfded32bb7..5d75304a339c 100644 --- a/sys/kern/kern_physio.c +++ b/sys/kern/kern_physio.c @@ -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 ioflag) 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, int ioflag) } } - dev->si_devsw->d_strategy(bp); + csw->d_strategy(bp); if (uio->uio_rw == UIO_READ) biowait(bp, "physrd"); else