On 3/21/2011 2:16 PM, Stefan Hajnoczi wrote: > On Mon, Mar 21, 2011 at 6:31 PM, Harsh Prateek Bora > <ha...@linux.vnet.ibm.com> wrote: >> The nwnames field in TWALK message is assumed to be >=0 and <= MAXWELEM >> which is defined as macro P9_MAXWELEM (16) in virtio-9p.h as per 9p2000 RFC. >> Appropriate changes are required in V9fsWalkState and v9fs_walk. >> >> Signed-off-by: Harsh Prateek Bora <ha...@linux.vnet.ibm.com> >> --- >> hw/9pfs/virtio-9p.c | 5 ++++- >> hw/9pfs/virtio-9p.h | 2 +- >> 2 files changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c >> index 9b44bd0..b782a19 100644 >> --- a/hw/9pfs/virtio-9p.c >> +++ b/hw/9pfs/virtio-9p.c >> @@ -1805,7 +1805,7 @@ static void v9fs_walk(V9fsState *s, V9fsPDU *pdu) >> vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "ddw", &fid, >> &newfid, &vs->nwnames); >> >> - if (vs->nwnames) { >> + if (vs->nwnames <= P9_MAXWELEM) { >> vs->wnames = qemu_mallocz(sizeof(vs->wnames[0]) * vs->nwnames); >> >> vs->qids = qemu_mallocz(sizeof(vs->qids[0]) * vs->nwnames); >> @@ -1814,6 +1814,9 @@ static void v9fs_walk(V9fsState *s, V9fsPDU *pdu) >> vs->offset += pdu_unmarshal(vs->pdu, vs->offset, "s", >> &vs->wnames[i]); >> } >> + } else { >> + err = -EINVAL; vs->nwnames = 0; will take care of v9fs_walk_complete() issue Stefan brought up. >> + goto out; >> } > > v9fs_walk_complete() will attempt to free wnames, qids, and the wnames > strings. Freeing the strings will crash because we're indexing into > an array based off a NULL pointer. > > It would be very handy to have a PDU-level test suite. You could then > construct a PDU with an invalid nwnames field and exercise this code > path. Perhaps a debug ioctl in Linux v9fs that allows a userspace > tool to pass PDUs through will do?
Ioctl way was ruled out in the past discussion. But yes we have in plan on to introduce a test suite of this kind. Malahal (who is on vacation) will start this work from early April. Thanks, JV > > Stefan