From: Zhang Xiaoxu zhangxiaoxu5@huawei.com

commit d527f51331cace562393a8038d870b3e9916686f upstream.

There is a UAF when xfstests on cifs:

BUG: KASAN: use-after-free in smb2_is_network_name_deleted+0x27/0x160 Read of size 4 at addr ffff88810103fc08 by task cifsd/923

CPU: 1 PID: 923 Comm: cifsd Not tainted 6.1.0-rc4+ #45 ... Call Trace: <TASK> dump_stack_lvl+0x34/0x44 print_report+0x171/0x472 kasan_report+0xad/0x130 kasan_check_range+0x145/0x1a0 smb2_is_network_name_deleted+0x27/0x160 cifs_demultiplex_thread.cold+0x172/0x5a4 kthread+0x165/0x1a0 ret_from_fork+0x1f/0x30 </TASK>

Allocated by task 923: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_slab_alloc+0x54/0x60 kmem_cache_alloc+0x147/0x320 mempool_alloc+0xe1/0x260 cifs_small_buf_get+0x24/0x60 allocate_buffers+0xa1/0x1c0 cifs_demultiplex_thread+0x199/0x10d0 kthread+0x165/0x1a0 ret_from_fork+0x1f/0x30

Freed by task 921: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x40 ____kasan_slab_free+0x143/0x1b0 kmem_cache_free+0xe3/0x4d0 cifs_small_buf_release+0x29/0x90 SMB2_negotiate+0x8b7/0x1c60 smb2_negotiate+0x51/0x70 cifs_negotiate_protocol+0xf0/0x160 cifs_get_smb_ses+0x5fa/0x13c0 mount_get_conns+0x7a/0x750 cifs_mount+0x103/0xd00 cifs_smb3_do_mount+0x1dd/0xcb0 smb3_get_tree+0x1d5/0x300 vfs_get_tree+0x41/0xf0 path_mount+0x9b3/0xdd0 __x64_sys_mount+0x190/0x1d0 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0

The UAF is because:

mount(pid: 921) | cifsd(pid: 923) -------------------------------|------------------------------- | cifs_demultiplex_thread SMB2_negotiate | cifs_send_recv | compound_send_recv | smb_send_rqst | wait_for_response | wait_event_state [1] | | standard_receive3 | cifs_handle_standard | handle_mid | mid->resp_buf = buf; [2] | dequeue_mid [3] KILL the process [4] | resp_iov[i].iov_base = buf | free_rsp_buf [5] | | is_network_name_deleted [6] | callback

1. After send request to server, wait the response until mid->mid_state != SUBMITTED; 2. Receive response from server, and set it to mid; 3. Set the mid state to RECEIVED; 4. Kill the process, the mid state already RECEIVED, get 0; 5. Handle and release the negotiate response; 6. UAF.

It can be easily reproduce with add some delay in [3] - [6].

Only sync call has the problem since async call's callback is executed in cifsd process.

Add an extra state to mark the mid state to READY before wakeup the waitter, then it can get the resp safely.

Fixes: ec637e3ffb6b ("[CIFS] Avoid extra large buffer allocation (and memcpy) in cifs_readpages") Reviewed-by: Paulo Alcantara (SUSE) pc@manguebit.com Signed-off-by: Zhang Xiaoxu zhangxiaoxu5@huawei.com Signed-off-by: Steve French stfrench@microsoft.com [fs/cifs was moved to fs/smb/client since 38c8a9a52082 ("smb: move client and server files to common directory fs/smb"). We apply the patch to fs/cifs with some minor context changes.] Signed-off-by: He Zhe zhe.he@windriver.com Signed-off-by: Xiangyu Chen xiangyu.chen@windriver.com --- Build test passed. --- fs/cifs/cifsglob.h | 1 + fs/cifs/transport.c | 34 +++++++++++++++++++++++----------- 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index 2ee67a27020d..8bd5d528244e 100644 --- a/fs/cifs/cifsglob.h +++ b/fs/cifs/cifsglob.h @@ -1719,6 +1719,7 @@ static inline bool is_retryable_error(int error) #define MID_RETRY_NEEDED 8 /* session closed while this request out */ #define MID_RESPONSE_MALFORMED 0x10 #define MID_SHUTDOWN 0x20 +#define MID_RESPONSE_READY 0x40 /* ready for other process handle the rsp */

/* Flags */ #define MID_WAIT_CANCELLED 1 /* Cancelled while waiting for response */ diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c index 49b7edbe3497..8cf12c106afa 100644 --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -34,6 +34,8 @@ void cifs_wake_up_task(struct mid_q_entry *mid) { + if (mid->mid_state == MID_RESPONSE_RECEIVED) + mid->mid_state = MID_RESPONSE_READY; wake_up_process(mid->callback_data); }

@@ -86,7 +88,8 @@ static void _cifs_mid_q_entry_release(struct kref *refcount) struct TCP_Server_Info *server = midEntry->server;

if (midEntry->resp_buf && (midEntry->mid_flags & MID_WAIT_CANCELLED) && - midEntry->mid_state == MID_RESPONSE_RECEIVED && + (midEntry->mid_state == MID_RESPONSE_RECEIVED || + midEntry->mid_state == MID_RESPONSE_READY) && server->ops->handle_cancelled_mid) server->ops->handle_cancelled_mid(midEntry, server);

@@ -762,7 +765,8 @@ wait_for_response(struct TCP_Server_Info *server, struct mid_q_entry *midQ) int error;

error = wait_event_freezekillable_unsafe(server->response_q, - midQ->mid_state != MID_REQUEST_SUBMITTED); + midQ->mid_state != MID_REQUEST_SUBMITTED && + midQ->mid_state != MID_RESPONSE_RECEIVED); if (error < 0) return -ERESTARTSYS;

@@ -914,7 +918,7 @@ cifs_sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server)

spin_lock(&GlobalMid_Lock); switch (mid->mid_state) { - case MID_RESPONSE_RECEIVED: + case MID_RESPONSE_READY: spin_unlock(&GlobalMid_Lock); return rc; case MID_RETRY_NEEDED: @@ -1013,6 +1017,9 @@ cifs_compound_callback(struct mid_q_entry *mid) credits.instance = server->reconnect_instance;

add_credits(server, &credits, mid->optype); + + if (mid->mid_state == MID_RESPONSE_RECEIVED) + mid->mid_state = MID_RESPONSE_READY; }

static void @@ -1204,7 +1211,8 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, send_cancel(server, &rqst[i], midQ[i]); spin_lock(&GlobalMid_Lock); midQ[i]->mid_flags |= MID_WAIT_CANCELLED; - if (midQ[i]->mid_state == MID_REQUEST_SUBMITTED) { + if (midQ[i]->mid_state == MID_REQUEST_SUBMITTED || + midQ[i]->mid_state == MID_RESPONSE_RECEIVED) { midQ[i]->callback = cifs_cancelled_callback; cancelled_mid[i] = true; credits[i].value = 0; @@ -1225,7 +1233,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses, }

if (!midQ[i]->resp_buf || - midQ[i]->mid_state != MID_RESPONSE_RECEIVED) { + midQ[i]->mid_state != MID_RESPONSE_READY) { rc = -EIO; cifs_dbg(FYI, "Bad MID state?\n"); goto out; @@ -1404,7 +1412,8 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses, if (rc != 0) { send_cancel(server, &rqst, midQ); spin_lock(&GlobalMid_Lock); - if (midQ->mid_state == MID_REQUEST_SUBMITTED) { + if (midQ->mid_state == MID_REQUEST_SUBMITTED || + midQ->mid_state == MID_RESPONSE_RECEIVED) { /* no longer considered to be "in-flight" */ midQ->callback = DeleteMidQEntry; spin_unlock(&GlobalMid_Lock); @@ -1421,7 +1430,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses, }

if (!midQ->resp_buf || !out_buf || - midQ->mid_state != MID_RESPONSE_RECEIVED) { + midQ->mid_state != MID_RESPONSE_READY) { rc = -EIO; cifs_server_dbg(VFS, "Bad MID state?\n"); goto out; @@ -1541,13 +1550,15 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon,

/* Wait for a reply - allow signals to interrupt. */ rc = wait_event_interruptible(server->response_q, - (!(midQ->mid_state == MID_REQUEST_SUBMITTED)) || + (!(midQ->mid_state == MID_REQUEST_SUBMITTED || + midQ->mid_state == MID_RESPONSE_RECEIVED)) || ((server->tcpStatus != CifsGood) && (server->tcpStatus != CifsNew)));

/* Were we interrupted by a signal ? */ if ((rc == -ERESTARTSYS) && - (midQ->mid_state == MID_REQUEST_SUBMITTED) && + (midQ->mid_state == MID_REQUEST_SUBMITTED || + midQ->mid_state == MID_RESPONSE_RECEIVED) && ((server->tcpStatus == CifsGood) || (server->tcpStatus == CifsNew))) {

@@ -1577,7 +1588,8 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon, if (rc) { send_cancel(server, &rqst, midQ); spin_lock(&GlobalMid_Lock); - if (midQ->mid_state == MID_REQUEST_SUBMITTED) { + if (midQ->mid_state == MID_REQUEST_SUBMITTED || + midQ->mid_state == MID_RESPONSE_RECEIVED) { /* no longer considered to be "in-flight" */ midQ->callback = DeleteMidQEntry; spin_unlock(&GlobalMid_Lock); @@ -1595,7 +1607,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifs_tcon *tcon, return rc;

/* rcvd frame is ok */ - if (out_buf == NULL || midQ->mid_state != MID_RESPONSE_RECEIVED) { + if (out_buf == NULL || midQ->mid_state != MID_RESPONSE_READY) { rc = -EIO; cifs_tcon_dbg(VFS, "Bad MID state?\n"); goto out;