From: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
[ Upstream commit 37020bbb71d911431e16c2c940b97cf86ae4f2f6 ]
The xarray iteration only holds the RCU read lock and thus may encounter
XA_RETRY_ENTRY if there's process modifying the xarray concurrently.
This will cause oops when referring to the invalid entry.
Fix this by adding the missing xas_retry(), which will make the
iteration wind back to the root node if XA_RETRY_ENTRY is encountered.
Fixes: d435d53228dd ("erofs: change to use asynchronous io for fscache readpage/readahead")
Suggested-by: David Howells <dhowells@xxxxxxxxxx>
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Reviewed-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221114121943.29987-1-jefflexu@xxxxxxxxxxxxxxxxx
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/erofs/fscache.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 79af25f0a56c..46ab2b3f9a3c 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -69,11 +69,15 @@ static void erofs_fscache_rreq_unlock_folios(struct netfs_io_request *rreq)
rcu_read_lock();
xas_for_each(&xas, folio, last_page) {
- unsigned int pgpos =
- (folio_index(folio) - start_page) * PAGE_SIZE;
- unsigned int pgend = pgpos + folio_size(folio);
+ unsigned int pgpos, pgend;
bool pg_failed = false;
+ if (xas_retry(&xas, folio))
+ continue;
+
+ pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
+ pgend = pgpos + folio_size(folio);
+
for (;;) {
if (!subreq) {
pg_failed = true;
--
2.35.1
