linux-kernel - [PATCH v2] erofs: fix missing xas

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20221114121943.29987-1-jefflexu@linux.alibaba.com>
Date:   Mon, 14 Nov 2022 20:19:43 +0800
From:   Jingbo Xu <jefflexu@...ux.alibaba.com>
To:     xiang@...nel.org, chao@...nel.org, yinxin.x@...edance.com,
        linux-erofs@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, dhowells@...hat.com
Subject: [PATCH v2] erofs: fix missing xas_retry() in fscache mode

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@...hat.com>
Reviewed-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@...edance.com>
Signed-off-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
---
v2:
- update the commit message suggested by David
- add "Suggested-by" tag, as this patch actually fixes the same issue
  as that fixed by David's patch [1]. Sorry I forgot in v1 ;-\
- add "Reviewed-by" tags

[1] https://lore.kernel.org/lkml/084d78a4-6052-f2ec-72f2-af9c4979f5dc@linux.alibaba.com/T/#m036d0221dacde491a1bcf2f4428e8b1450179df9
---
 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 fe05bc51f9f2..458c1c70ef30 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -75,11 +75,15 @@ 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;
-- 
2.19.1.6.gb485710b