In tcmu_blocks_release, lock_page() is called to prevent a race causing
possible data corruption. Since lock_page() might sleep, calling it
while holding XArray lock is a bug.
To fix the bug switch to XArray normal API by replacing the xas_for_each
with xa_for_each_range. Since normal API does its own handling of
XArray locking, now the xas_lock and xas_unlock around the loop are
obsolete.
While keeping the code short and simple, the switch to normal API slows
down the loop slightly, which is acceptable since tcmu_blocks_release is
not relevant for performance.
Fixes: bb9b9eb0ae2e ("scsi: target: tcmu: Fix possible data corruption")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Bodo Stroesser <bostroesser@xxxxxxxxx>
---
drivers/target/target_core_user.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index b1fd06edea59..3deaeecb712e 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1661,13 +1661,14 @@ static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
static u32 tcmu_blocks_release(struct tcmu_dev *udev, unsigned long first,
unsigned long last)
{
- XA_STATE(xas, &udev->data_pages, first * udev->data_pages_per_blk);
struct page *page;
+ unsigned long dpi;
u32 pages_freed = 0;
- xas_lock(&xas);
- xas_for_each(&xas, page, (last + 1) * udev->data_pages_per_blk - 1) {
- xas_store(&xas, NULL);
+ first = first * udev->data_pages_per_blk;
+ last = (last + 1) * udev->data_pages_per_blk - 1;
+ xa_for_each_range(&udev->data_pages, dpi, page, first, last) {
+ xa_erase(&udev->data_pages, dpi);
/*
* While reaching here there may be page faults occurring on
* the to-be-released pages. A race condition may occur if
@@ -1691,7 +1692,6 @@ static u32 tcmu_blocks_release(struct tcmu_dev *udev, unsigned long first,
__free_page(page);
pages_freed++;
}
- xas_unlock(&xas);
atomic_sub(pages_freed, &global_page_count);
--
2.12.3
