From: Jingbo Xu jefflexu@linux.alibaba.com
[ 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@redhat.com Reviewed-by: Gao Xiang hsiangkao@linux.alibaba.com Reviewed-by: Jia Zhu zhujia.zj@bytedance.com Signed-off-by: Jingbo Xu jefflexu@linux.alibaba.com Link: https://lore.kernel.org/r/20221114121943.29987-1-jefflexu@linux.alibaba.com Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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;