[PATCH 5.15 070/177] dmaengine: idxd: fix missed completion on abort path

Greg Kroah-Hartman
2021-12-20T14:58:22Z

From: Dave Jiang <dave.jiang@intel.com>

[ Upstream commit 8affd8a4b5ce356c8900cfb037674f3a4a11fbdb ]

Ming reported that with the abort path of the descriptor submission, there
can be a window where a completed descriptor can be missed to be completed
by the irq completion thread:

CPU A CPU B
Submit (successful)

Submit (fail)
irq_process_work_list() // empty

llist_abort_desc()
// remove all descs from pending list

irq_process_pending_llist() // empty
exit idxd_wq_thread() with no processing

Add opportunistic descriptor completion in the abort path in order to
remove the missed completion.

Fixes: 6b4b87f2c31a ("dmaengine: idxd: fix submission race window")
Reported-by: Ming Li <ming4.li@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163898288714.443911.16084982766671976640.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/idxd/submit.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/idxd/submit.c b/drivers/dma/idxd/submit.c
index de76fb4abac24..83452fbbb168b 100644
--- a/drivers/dma/idxd/submit.c
+++ b/drivers/dma/idxd/submit.c
@@ -106,6 +106,7 @@ static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
{
struct idxd_desc *d, *t, *found = NULL;
struct llist_node *head;
+ LIST_HEAD(flist);

desc->completion->status = IDXD_COMP_DESC_ABORT;
/*
@@ -120,7 +121,11 @@ static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
found = desc;
continue;
}
- list_add_tail(&desc->list, &ie->work_list);
+
+ if (d->completion->status)
+ list_add_tail(&d->list, &flist);
+ else
+ list_add_tail(&d->list, &ie->work_list);
}
}

@@ -130,6 +135,17 @@ static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,

if (found)
complete_desc(found, IDXD_COMPLETE_ABORT);
+
+ /*
+ * complete_desc() will return desc to allocator and the desc can be
+ * acquired by a different process and the desc->list can be modified.
+ * Delete desc from list so the list trasversing does not get corrupted
+ * by the other process.
+ */
+ list_for_each_entry_safe(d, t, &flist, list) {
+ list_del_init(&d->list);
+ complete_desc(d, IDXD_COMPLETE_NORMAL);
+ }
}

int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
--
2.33.0