From 6e9a599b2709c19baaec6377e4868a96074fbb8a Mon Sep 17 00:00:00 2001 From: Steven Hartland Date: Sat, 27 Sep 2014 19:14:22 +0000 Subject: Use a local STAILQ for unlocked done CCB processing in ahci direct mode Previously it was possible for issues e.g. use after free, to result from processing the done queue while not holding the channel lock. While this should never happen in practice, unexpected code flows which result in two threads processing from the same queue may be possible. We now use a local STAILQ to prevent this ever being an issue. Sponsored by: Multiplay --- sys/dev/ahci/ahci.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/sys/dev/ahci/ahci.c b/sys/dev/ahci/ahci.c index 0c3197a3f7d3..69fa76bfab42 100644 --- a/sys/dev/ahci/ahci.c +++ b/sys/dev/ahci/ahci.c @@ -1126,6 +1126,7 @@ ahci_ch_intr_direct(void *arg) struct ahci_channel *ch = (struct ahci_channel *)arg; struct ccb_hdr *ccb_h; uint32_t istatus; + STAILQ_HEAD(, ccb_hdr) tmp_doneq = STAILQ_HEAD_INITIALIZER(tmp_doneq); /* Read interrupt statuses. */ istatus = ATA_INL(ch->r_mem, AHCI_P_IS); @@ -1136,9 +1137,14 @@ ahci_ch_intr_direct(void *arg) ch->batch = 1; ahci_ch_intr_main(ch, istatus); ch->batch = 0; + /* + * Prevent the possibility of issues caused by processing the queue + * while unlocked below by moving the contents to a local queue. + */ + STAILQ_CONCAT(&tmp_doneq, &ch->doneq); mtx_unlock(&ch->mtx); - while ((ccb_h = STAILQ_FIRST(&ch->doneq)) != NULL) { - STAILQ_REMOVE_HEAD(&ch->doneq, sim_links.stqe); + while ((ccb_h = STAILQ_FIRST(&tmp_doneq)) != NULL) { + STAILQ_REMOVE_HEAD(&tmp_doneq, sim_links.stqe); xpt_done_direct((union ccb *)ccb_h); } } -- cgit v1.2.3