linux-kernel - [RESEND PATCHv2 2/2] fs: dcache: Use READ_ONCE when accessing i_dir

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>] [<thread-prev] [day] [month] [year] [list]

Date:   Tue,  6 Mar 2018 19:05:06 +0000
From:   Will Deacon <will.deacon@....com>
To:     linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
        torvalds@...ux-foundation.org
Cc:     peterz@...radead.org, willy@...radead.org,
        linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>
Subject: [RESEND PATCHv2 2/2] fs: dcache: Use READ_ONCE when accessing i_dir_seq

i_dir_seq is subject to concurrent modification by a cmpxchg or
store-release operation, so ensure that the relaxed access in
d_alloc_parallel uses READ_ONCE.

Reported-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Will Deacon <will.deacon@....com>
---
 fs/dcache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b243deec298c..5716ab04e1db 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2502,7 +2502,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 	}
 
 	hlist_bl_lock(b);
-	if (unlikely(parent->d_inode->i_dir_seq != seq)) {
+	if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
 		hlist_bl_unlock(b);
 		rcu_read_unlock();
 		goto retry;
-- 
2.1.4