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[92.109.99.123]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-afdf24bc40dsm341995766b.109.2025.08.21.06.43.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Aug 2025 06:43:00 -0700 (PDT) From: Amir Goldstein To: Greg Kroah-Hartman Cc: Sasha Levin , stable@vger.kernel.org, linux-unionfs@vger.kernel.org, NeilBrown , syzbot+7836a68852a10ec3d790@syzkaller.appspotmail.com Subject: [PATCH] ovl: use I_MUTEX_PARENT when locking parent in ovl_create_temp() Date: Thu, 21 Aug 2025 15:42:44 +0200 Message-ID: <20250821134244.846376-1-amir73il@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: NeilBrown commit 5f1c8965e748c150d580a2ea8fbee1bd80d07a24 upstream. ovl_create_temp() treats "workdir" as a parent in which it creates an object so it should use I_MUTEX_PARENT. Prior to the commit identified below the lock was taken by the caller which sometimes used I_MUTEX_PARENT and sometimes used I_MUTEX_NORMAL. The use of I_MUTEX_NORMAL was incorrect but unfortunately copied into ovl_create_temp(). Note to backporters: This patch only applies after the last Fixes given below (post v6.16). To fix the bug in v6.7 and later the inode_lock() call in ovl_copy_up_workdir() needs to nest using I_MUTEX_PARENT. [Amir: backport to v6.16 when lock was taken by the callers] Link: https://lore.kernel.org/all/67a72070.050a0220.3d72c.0022.GAE@google.com/ Cc: stable@vger.kernel.org Reported-by: syzbot+7836a68852a10ec3d790@syzkaller.appspotmail.com Tested-by: syzbot+7836a68852a10ec3d790@syzkaller.appspotmail.com Fixes: c63e56a4a652 ("ovl: do not open/llseek lower file with upper sb_writers held") Fixes: d2c995581c7c ("ovl: Call ovl_create_temp() without lock held.") Signed-off-by: NeilBrown Signed-off-by: Amir Goldstein --- fs/overlayfs/copy_up.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index d7310fcf38881..c2263148ff20a 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -779,7 +779,7 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) return err; ovl_start_write(c->dentry); - inode_lock(wdir); + inode_lock_nested(wdir, I_MUTEX_PARENT); temp = ovl_create_temp(ofs, c->workdir, &cattr); inode_unlock(wdir); ovl_end_write(c->dentry); -- 2.50.1