From: Nalivayko Sergey Sergey.Nalivayko@kaspersky.com
[ Upstream commit 674b56aa57f9379854cb6798c3bbcef7e7b51ab7 ]
Syzkaller reports a KASAN issue as below:
general protection fault, probably for non-canonical address 0xfbd59c0000000021: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: maybe wild-memory-access in range [0xdead000000000108-0xdead00000000010f] CPU: 0 PID: 5083 Comm: syz-executor.2 Not tainted 6.1.134-syzkaller-00037-g855bd1d7d838 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:__list_del include/linux/list.h:114 [inline] RIP: 0010:__list_del_entry include/linux/list.h:137 [inline] RIP: 0010:list_del include/linux/list.h:148 [inline] RIP: 0010:p9_fd_cancelled+0xe9/0x200 net/9p/trans_fd.c:734
Call Trace: <TASK> p9_client_flush+0x351/0x440 net/9p/client.c:614 p9_client_rpc+0xb6b/0xc70 net/9p/client.c:734 p9_client_version net/9p/client.c:920 [inline] p9_client_create+0xb51/0x1240 net/9p/client.c:1027 v9fs_session_init+0x1f0/0x18f0 fs/9p/v9fs.c:408 v9fs_mount+0xba/0xcb0 fs/9p/vfs_super.c:126 legacy_get_tree+0x108/0x220 fs/fs_context.c:632 vfs_get_tree+0x8e/0x300 fs/super.c:1573 do_new_mount fs/namespace.c:3056 [inline] path_mount+0x6a6/0x1e90 fs/namespace.c:3386 do_mount fs/namespace.c:3399 [inline] __do_sys_mount fs/namespace.c:3607 [inline] __se_sys_mount fs/namespace.c:3584 [inline] __x64_sys_mount+0x283/0x300 fs/namespace.c:3584 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
This happens because of a race condition between:
- The 9p client sending an invalid flush request and later cleaning it up; - The 9p client in p9_read_work() canceled all pending requests.
Thread 1 Thread 2 ... p9_client_create() ... p9_fd_create() ... p9_conn_create() ... // start Thread 2 INIT_WORK(&m->rq, p9_read_work); p9_read_work() ... p9_client_rpc() ... ... p9_conn_cancel() ... spin_lock(&m->req_lock); ... p9_fd_cancelled() ... ... spin_unlock(&m->req_lock); // status rewrite p9_client_cb(m->client, req, REQ_STATUS_ERROR) // first remove list_del(&req->req_list); ...
spin_lock(&m->req_lock) ... // second remove list_del(&req->req_list); spin_unlock(&m->req_lock) ...
Commit 74d6a5d56629 ("9p/trans_fd: Fix concurrency del of req_list in p9_fd_cancelled/p9_read_work") fixes a concurrency issue in the 9p filesystem client where the req_list could be deleted simultaneously by both p9_read_work and p9_fd_cancelled functions, but for the case where req->status equals REQ_STATUS_RCVD.
Update the check for req->status in p9_fd_cancelled to skip processing not just received requests, but anything that is not SENT, as whatever changed the state from SENT also removed the request from its list.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: afd8d6541155 ("9P: Add cancelled() to the transport functions.") Cc: stable@vger.kernel.org Signed-off-by: Nalivayko Sergey Sergey.Nalivayko@kaspersky.com Message-ID: 20250715154815.3501030-1-Sergey.Nalivayko@kaspersky.com [updated the check from status == RECV || status == ERROR to status != SENT] Signed-off-by: Dominique Martinet asmadeus@codewreck.org [ replaced m->req_lock with client->lock ] Signed-off-by: Sasha Levin sashal@kernel.org --- net/9p/trans_fd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 63f4d2067059e..40d458c438df1 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -711,10 +711,10 @@ static int p9_fd_cancelled(struct p9_client *client, struct p9_req_t *req) p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);
spin_lock(&client->lock); - /* Ignore cancelled request if message has been received - * before lock. - */ - if (req->status == REQ_STATUS_RCVD) { + /* Ignore cancelled request if status changed since the request was + * processed in p9_client_flush() + */ + if (req->status != REQ_STATUS_SENT) { spin_unlock(&client->lock); return 0; }