From: Bodo Stroesser bostroesser@gmail.com
[ Upstream commit 325d5c5fb216674296f3902a8902b942da3adc5b ]
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 this, replace the xas_for_each() call with xa_for_each_range(). Since the latter does its own handling of XArray locking, the xas_lock() and xas_unlock() calls around the original loop are no longer necessary.
The switch to xa_for_each_range() slows down the loop slightly. This is acceptable since tcmu_blocks_release() is not relevant for performance.
Link: https://lore.kernel.org/r/20220517192913.21405-1-bostroesser@gmail.com Fixes: bb9b9eb0ae2e ("scsi: target: tcmu: Fix possible data corruption") Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Bodo Stroesser bostroesser@gmail.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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);