From 39d08d8903994076f41d97e6c1fa1e40eb4a5972 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 5 Sep 2024 20:27:25 +0200 Subject: [PATCH] dm-integrity: fix a race condition when accessing recalc_sector BugLink: https://bugs.launchpad.net/bugs/2086138 commit f8e1ca92e35e9041cc0a1bc226ef07a853a22de4 upstream. There's a race condition when accessing the variable ic->sb->recalc_sector. The function integrity_recalc writes to this variable when it makes some progress and the function dm_integrity_map_continue may read this variable concurrently. One problem is that on 32-bit architectures the 64-bit variable is not read and written atomically - it may be possible to read garbage if read races with write. Another problem is that memory accesses to this variable are not guarded with memory barriers. This commit fixes the race - it moves reading ic->sb->recalc_sector to an earlier place where we hold &ic->endio_wait.lock. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Koichiro Den Signed-off-by: Roxana Nicolescu --- drivers/md/dm-integrity.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c index 246ef6f6aae5..c8c78425dcef 100644 --- a/drivers/md/dm-integrity.c +++ b/drivers/md/dm-integrity.c @@ -2173,6 +2173,7 @@ static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map struct bio *bio = dm_bio_from_per_bio_data(dio, sizeof(struct dm_integrity_io)); unsigned int journal_section, journal_entry; unsigned int journal_read_pos; + sector_t recalc_sector; struct completion read_comp; bool discard_retried = false; bool need_sync_io = ic->internal_hash && dio->op == REQ_OP_READ; @@ -2313,6 +2314,7 @@ offload_to_thread: goto lock_retry; } } + recalc_sector = le64_to_cpu(ic->sb->recalc_sector); spin_unlock_irq(&ic->endio_wait.lock); if (unlikely(journal_read_pos != NOT_FOUND)) { @@ -2367,7 +2369,7 @@ offload_to_thread: if (need_sync_io) { wait_for_completion_io(&read_comp); if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING) && - dio->range.logical_sector + dio->range.n_sectors > le64_to_cpu(ic->sb->recalc_sector)) + dio->range.logical_sector + dio->range.n_sectors > recalc_sector) goto skip_check; if (ic->mode == 'B') { if (!block_bitmap_op(ic, ic->recalc_bitmap, dio->range.logical_sector,