From 11c10956515b8ec44cf4f2a7b9d8bf8b9dc05ec4 Mon Sep 17 00:00:00 2001 From: Zhengchao Shao Date: Thu, 10 Nov 2022 20:26:06 +0800 Subject: 9p/fd: fix issue of list_del corruption in p9_fd_cancel() Syz reported the following issue: kernel BUG at lib/list_debug.c:53! invalid opcode: 0000 [#1] PREEMPT SMP KASAN RIP: 0010:__list_del_entry_valid.cold+0x5c/0x72 Call Trace: p9_fd_cancel+0xb1/0x270 p9_client_rpc+0x8ea/0xba0 p9_client_create+0x9c0/0xed0 v9fs_session_init+0x1e0/0x1620 v9fs_mount+0xba/0xb80 legacy_get_tree+0x103/0x200 vfs_get_tree+0x89/0x2d0 path_mount+0x4c0/0x1ac0 __x64_sys_mount+0x33b/0x430 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 The process is as follows: Thread A: Thread B: p9_poll_workfn() p9_client_create() ... ... p9_conn_cancel() p9_fd_cancel() list_del() ... ... list_del() //list_del corruption There is no lock protection when deleting list in p9_conn_cancel(). After deleting list in Thread A, thread B will delete the same list again. It will cause issue of list_del corruption. Setting req->status to REQ_STATUS_ERROR under lock prevents other cleanup paths from trying to manipulate req_list. The other thread can safely check req->status because it still holds a reference to req at this point. Link: https://lkml.kernel.org/r/20221110122606.383352-1-shaozhengchao@huawei.com Fixes: 52f1c45dde91 ("9p: trans_fd/p9_conn_cancel: drop client lock earlier") Reported-by: syzbot+9b69b8d10ab4a7d88056@syzkaller.appspotmail.com Signed-off-by: Zhengchao Shao [Dominique: add description of the fix in commit message] Signed-off-by: Dominique Martinet --- net/9p/trans_fd.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net') diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 56a186768750..bd28e63d7666 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -202,9 +202,11 @@ static void p9_conn_cancel(struct p9_conn *m, int err) list_for_each_entry_safe(req, rtmp, &m->req_list, req_list) { list_move(&req->req_list, &cancel_list); + req->status = REQ_STATUS_ERROR; } list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) { list_move(&req->req_list, &cancel_list); + req->status = REQ_STATUS_ERROR; } spin_unlock(&m->req_lock); -- cgit