On Wed, Nov 06, 2019 at 10:16:35AM -0800, Pavel Shilovsky wrote:
Commit abe57073d08c1 ("CIFS: Fix retry mid list corruption on reconnects") upstream.
When the client hits reconnect it iterates over the mid pending queue marking entries for retry and moving them to a temporary list to issue callbacks later without holding GlobalMid_Lock. In the same time there is no guarantee that mids can't be removed from the temporary list or even freed completely by another thread. It may cause a temporary list corruption:
[ 430.454897] list_del corruption. prev->next should be ffff98d3a8f316c0, but was 2e885cb266355469 [ 430.464668] ------------[ cut here ]------------ [ 430.466569] kernel BUG at lib/list_debug.c:51! [ 430.468476] invalid opcode: 0000 [#1] SMP PTI [ 430.470286] CPU: 0 PID: 13267 Comm: cifsd Kdump: loaded Not tainted 5.4.0-rc3+ #19 [ 430.473472] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 430.475872] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55 ... [ 430.510426] Call Trace: [ 430.511500] cifs_reconnect+0x25e/0x610 [cifs] [ 430.513350] cifs_readv_from_socket+0x220/0x250 [cifs] [ 430.515464] cifs_read_from_socket+0x4a/0x70 [cifs] [ 430.517452] ? try_to_wake_up+0x212/0x650 [ 430.519122] ? cifs_small_buf_get+0x16/0x30 [cifs] [ 430.521086] ? allocate_buffers+0x66/0x120 [cifs] [ 430.523019] cifs_demultiplex_thread+0xdc/0xc30 [cifs] [ 430.525116] kthread+0xfb/0x130 [ 430.526421] ? cifs_handle_standard+0x190/0x190 [cifs] [ 430.528514] ? kthread_park+0x90/0x90 [ 430.530019] ret_from_fork+0x35/0x40
Fix this by obtaining extra references for mids being retried and marking them as MID_DELETED which indicates that such a mid has been dequeued from the pending list.
Also move mid cleanup logic from DeleteMidQEntry to _cifs_mid_q_entry_release which is called when the last reference to a particular mid is put. This allows to avoid any use-after-free of response buffers.
The patch needs to be backported to stable kernels. A stable tag is not mentioned below because the patch doesn't apply cleanly to any actively maintained stable kernel.
Cc: Stable stable@vger.kernel.org # 5.3.x Reviewed-by: Ronnie Sahlberg lsahlber@redhat.com Reviewed-and-tested-by: David Wysochanski dwysocha@redhat.com Signed-off-by: Pavel Shilovsky pshilov@microsoft.com
fs/cifs/connect.c | 10 +++++++++- fs/cifs/transport.c | 42 +++++++++++++++++++++++------------------- 2 files changed, 32 insertions(+), 20 deletions(-)
Now queued up, thanks.
greg k-h