kernel/linux.git/drivers/xen, branch v4.19.77

xen/pciback: remove set but not used variable 'old_state'

2019-08-25T08:47:52+00:00

[ Upstream commit 09e088a4903bd0dd911b4f1732b250130cdaffed ] Fixes gcc '-Wunused-but-set-variable' warning: drivers/xen/xen-pciback/conf_space_capability.c: In function pm_ctrl_write: drivers/xen/xen-pciback/conf_space_capability.c:119:25: warning: variable old_state set but not used [-Wunused-but-set-variable] It is never used so can be removed. Reported-by: Hulk Robot Signed-off-by: YueHaibing Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin

xen/swiotlb: fix condition for calling xen_destroy_contiguous_region()

2019-08-06T17:06:55+00:00

commit 50f6393f9654c561df4cdcf8e6cfba7260143601 upstream. The condition in xen_swiotlb_free_coherent() for deciding whether to call xen_destroy_contiguous_region() is wrong: in case the region to be freed is not contiguous calling xen_destroy_contiguous_region() is the wrong thing to do: it would result in inconsistent mappings of multiple PFNs to the same MFN. This will lead to various strange crashes or data corruption. Instead of calling xen_destroy_contiguous_region() in that case a warning should be issued as that situation should never occur. Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Reviewed-by: Jan Beulich Acked-by: Konrad Rzeszutek Wilk Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman

xen/events: fix binding user event channels to cpus

2019-07-26T07:14:25+00:00

commit bce5963bcb4f9934faa52be323994511d59fd13c upstream. When binding an interdomain event channel to a vcpu via IOCTL_EVTCHN_BIND_INTERDOMAIN not only the event channel needs to be bound, but the affinity of the associated IRQi must be changed, too. Otherwise the IRQ and the event channel won't be moved to another vcpu in case the original vcpu they were bound to is going offline. Cc: # 4.13 Fixes: c48f64ab472389df ("xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU") Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman

xen: let alloc_xenballooned_pages() fail if not enough memory free

2019-07-26T07:14:18+00:00

commit a1078e821b605813b63bf6bca414a85f804d5c66 upstream. Instead of trying to allocate pages with GFP_USER in add_ballooned_pages() check the available free memory via si_mem_available(). GFP_USER is far less limiting memory exhaustion than the test via si_mem_available(). This will avoid dom0 running out of memory due to excessive foreign page mappings especially on ARM and on x86 in PVH mode, as those don't have a pre-ballooned area which can be used for foreign mappings. As the normal ballooning suffers from the same problem don't balloon down more than si_mem_available() pages in one iteration. At the same time limit the default maximum number of retries. This is part of XSA-300. Signed-off-by: Juergen Gross Signed-off-by: Greg Kroah-Hartman

xenbus: Avoid deadlock during suspend due to open transactions

2019-06-22T06:15:19+00:00

[ Upstream commit d10e0cc113c9e1b64b5c6e3db37b5c839794f3df ] During a suspend/resume, the xenwatch thread waits for all outstanding xenstore requests and transactions to complete. This does not work correctly for transactions started by userspace because it waits for them to complete after freezing userspace threads which means the transactions have no way of completing, resulting in a deadlock. This is trivial to reproduce by running this script and then suspending the VM: import pyxs, time c = pyxs.client.Client(xen_bus_path="/dev/xen/xenbus") c.connect() c.transaction() time.sleep(3600) Even if this deadlock were resolved, misbehaving userspace should not prevent a VM from being migrated. So, instead of waiting for these transactions to complete before suspending, store the current generation id for each transaction when it is started. The global generation id is incremented during resume. If the caller commits the transaction and the generation id does not match the current generation id, return EAGAIN so that they try again. If the transaction was instead discarded, return OK since no changes were made anyway. This only affects users of the xenbus file interface. In-kernel users of xenbus are assumed to be well-behaved and complete all transactions before freezing. Signed-off-by: Ross Lagerwall Reviewed-by: Juergen Gross Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin

xen/pvcalls: Remove set but not used variable

2019-06-22T06:15:19+00:00

[ Upstream commit 41349672e3cbc2e8349831f21253509c3415aa2b ] Fixes gcc '-Wunused-but-set-variable' warning: drivers/xen/pvcalls-front.c: In function pvcalls_front_sendmsg: drivers/xen/pvcalls-front.c:543:25: warning: variable bedata set but not used [-Wunused-but-set-variable] drivers/xen/pvcalls-front.c: In function pvcalls_front_recvmsg: drivers/xen/pvcalls-front.c:638:25: warning: variable bedata set but not used [-Wunused-but-set-variable] They are never used since introduction. Signed-off-by: YueHaibing Reviewed-by: Juergen Gross Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin

xen/pciback: Don't disable PCI_COMMAND on PCI device reset.

2019-06-04T06:02:34+00:00

commit 7681f31ec9cdacab4fd10570be924f2cef6669ba upstream. There is no need for this at all. Worst it means that if the guest tries to write to BARs it could lead (on certain platforms) to PCI SERR errors. Please note that with af6fc858a35b90e89ea7a7ee58e66628c55c776b "xen-pciback: limit guest control of command register" a guest is still allowed to enable those control bits (safely), but is not allowed to disable them and that therefore a well behaved frontend which enables things before using them will still function correctly. This is done via an write to the configuration register 0x4 which triggers on the backend side: command_write \- pci_enable_device \- pci_enable_device_flags \- do_pci_enable_device \- pcibios_enable_device \-pci_enable_resourcess [which enables the PCI_COMMAND_MEMORY|PCI_COMMAND_IO] However guests (and drivers) which don't do this could cause problems, including the security issues which XSA-120 sought to address. Reported-by: Jan Beulich Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: Prarit Bhargava Signed-off-by: Juergen Gross Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock

2019-05-08T05:21:51+00:00

[ Upstream commit 10dce8af34226d90fa56746a934f8da5dcdba3df ] Commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per POSIX") added locking for file.f_pos access and in particular made concurrent read and write not possible - now both those functions take f_pos lock for the whole run, and so if e.g. a read is blocked waiting for data, write will deadlock waiting for that read to complete. This caused regression for stream-like files where previously read and write could run simultaneously, but after that patch could not do so anymore. See e.g. commit 581d21a2d02a ("xenbus: fix deadlock on writes to /proc/xen/xenbus") which fixes such regression for particular case of /proc/xen/xenbus. The patch that added f_pos lock in 2014 did so to guarantee POSIX thread safety for read/write/lseek and added the locking to file descriptors of all regular files. In 2014 that thread-safety problem was not new as it was already discussed earlier in 2006. However even though 2006'th version of Linus's patch was adding f_pos locking "only for files that are marked seekable with FMODE_LSEEK (thus avoiding the stream-like objects like pipes and sockets)", the 2014 version - the one that actually made it into the tree as 9c225f2655e3 - is doing so irregardless of whether a file is seekable or not. See https://lore.kernel.org/lkml/53022DB1.4070805@gmail.com/ https://lwn.net/Articles/180387 https://lwn.net/Articles/180396 for historic context. The reason that it did so is, probably, that there are many files that are marked non-seekable, but e.g. their read implementation actually depends on knowing current position to correctly handle the read. Some examples: kernel/power/user.c snapshot_read fs/debugfs/file.c u32_array_read fs/fuse/control.c fuse_conn_waiting_read + ... drivers/hwmon/asus_atk0110.c atk_debugfs_ggrp_read arch/s390/hypfs/inode.c hypfs_read_iter ... Despite that, many nonseekable_open users implement read and write with pure stream semantics - they don't depend on passed ppos at all. And for those cases where read could wait for something inside, it creates a situation similar to xenbus - the write could be never made to go until read is done, and read is waiting for some, potentially external, event, for potentially unbounded time -> deadlock. Besides xenbus, there are 14 such places in the kernel that I've found with semantic patch (see below): drivers/xen/evtchn.c:667:8-24: ERROR: evtchn_fops: .read() can deadlock .write() drivers/isdn/capi/capi.c:963:8-24: ERROR: capi_fops: .read() can deadlock .write() drivers/input/evdev.c:527:1-17: ERROR: evdev_fops: .read() can deadlock .write() drivers/char/pcmcia/cm4000_cs.c:1685:7-23: ERROR: cm4000_fops: .read() can deadlock .write() net/rfkill/core.c:1146:8-24: ERROR: rfkill_fops: .read() can deadlock .write() drivers/s390/char/fs3270.c:488:1-17: ERROR: fs3270_fops: .read() can deadlock .write() drivers/usb/misc/ldusb.c:310:1-17: ERROR: ld_usb_fops: .read() can deadlock .write() drivers/hid/uhid.c:635:1-17: ERROR: uhid_fops: .read() can deadlock .write() net/batman-adv/icmp_socket.c:80:1-17: ERROR: batadv_fops: .read() can deadlock .write() drivers/media/rc/lirc_dev.c:198:1-17: ERROR: lirc_fops: .read() can deadlock .write() drivers/leds/uleds.c:77:1-17: ERROR: uleds_fops: .read() can deadlock .write() drivers/input/misc/uinput.c:400:1-17: ERROR: uinput_fops: .read() can deadlock .write() drivers/infiniband/core/user_mad.c:985:7-23: ERROR: umad_fops: .read() can deadlock .write() drivers/gnss/core.c:45:1-17: ERROR: gnss_fops: .read() can deadlock .write() In addition to the cases above another regression caused by f_pos locking is that now FUSE filesystems that implement open with FOPEN_NONSEEKABLE flag, can no longer implement bidirectional stream-like files - for the same reason as above e.g. read can deadlock write locking on file.f_pos in the kernel. FUSE's FOPEN_NONSEEKABLE was added in 2008 in a7c1b990f715 ("fuse: implement nonseekable open") to support OSSPD. OSSPD implements /dev/dsp in userspace with FOPEN_NONSEEKABLE flag, with corresponding read and write routines not depending on current position at all, and with both read and write being potentially blocking operations: See https://github.com/libfuse/osspd https://lwn.net/Articles/308445 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1406 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1438-L1477 https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1479-L1510 Corresponding libfuse example/test also describes FOPEN_NONSEEKABLE as "somewhat pipe-like files ..." with read handler not using offset. However that test implements only read without write and cannot exercise the deadlock scenario: https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L124-L131 https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L146-L163 https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L209-L216 I've actually hit the read vs write deadlock for real while implementing my FUSE filesystem where there is /head/watch file, for which open creates separate bidirectional socket-like stream in between filesystem and its user with both read and write being later performed simultaneously. And there it is semantically not easy to split the stream into two separate read-only and write-only channels: https://lab.nexedi.com/kirr/wendelin.core/blob/f13aa600/wcfs/wcfs.go#L88-169 Let's fix this regression. The plan is: 1. We can't change nonseekable_open to include &~FMODE_ATOMIC_POS - doing so would break many in-kernel nonseekable_open users which actually use ppos in read/write handlers. 2. Add stream_open() to kernel to open stream-like non-seekable file descriptors. Read and write on such file descriptors would never use nor change ppos. And with that property on stream-like files read and write will be running without taking f_pos lock - i.e. read and write could be running simultaneously. 3. With semantic patch search and convert to stream_open all in-kernel nonseekable_open users for which read and write actually do not depend on ppos and where there is no other methods in file_operations which assume @offset access. 4. Add FOPEN_STREAM to fs/fuse/ and open in-kernel file-descriptors via steam_open if that bit is present in filesystem open reply. It was tempting to change fs/fuse/ open handler to use stream_open instead of nonseekable_open on just FOPEN_NONSEEKABLE flags, but grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE, and in particular GVFS which actually uses offset in its read and write handlers https://codesearch.debian.net/search?q=-%3Enonseekable+%3D https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080 https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346 https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481 so if we would do such a change it will break a real user. 5. Add stream_open and FOPEN_STREAM handling to stable kernels starting from v3.14+ (the kernel where 9c225f2655 first appeared). This will allow to patch OSSPD and other FUSE filesystems that provide stream-like files to return FOPEN_STREAM | FOPEN_NONSEEKABLE in their open handler and this way avoid the deadlock on all kernel versions. This should work because fs/fuse/ ignores unknown open flags returned from a filesystem and so passing FOPEN_STREAM to a kernel that is not aware of this flag cannot hurt. In turn the kernel that is not aware of FOPEN_STREAM will be < v3.14 where just FOPEN_NONSEEKABLE is sufficient to implement streams without read vs write deadlock. This patch adds stream_open, converts /proc/xen/xenbus to it and adds semantic patch to automatically locate in-kernel places that are either required to be converted due to read vs write deadlock, or that are just safe to be converted because read and write do not use ppos and there are no other funky methods in file_operations. Regarding semantic patch I've verified each generated change manually - that it is correct to convert - and each other nonseekable_open instance left - that it is either not correct to convert there, or that it is not converted due to current stream_open.cocci limitations. The script also does not convert files that should be valid to convert, but that currently have .llseek = noop_llseek or generic_file_llseek for unknown reason despite file being opened with nonseekable_open (e.g. drivers/input/mousedev.c) Cc: Michael Kerrisk Cc: Yongzhi Pan Cc: Jonathan Corbet Cc: David Vrabel Cc: Juergen Gross Cc: Miklos Szeredi Cc: Tejun Heo Cc: Kirill Tkhai Cc: Arnd Bergmann Cc: Christoph Hellwig Cc: Greg Kroah-Hartman Cc: Julia Lawall Cc: Nikolaus Rath Cc: Han-Wen Nienhuys Signed-off-by: Kirill Smelkov Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

xen/gntdev: Do not destroy context while dma-bufs are in use

2019-04-05T20:33:06+00:00

[ Upstream commit fa13e665e02874c0a5f4d06d6967ae34a6cb3d6a ] If there are exported DMA buffers which are still in use and grant device is closed by either normal user-space close or by a signal this leads to the grant device context to be destroyed, thus making it not possible to correctly destroy those exported buffers when they are returned back to gntdev and makes the module crash: [ 339.617540] [] dmabuf_exp_ops_release+0x40/0xa8 [ 339.617560] [] dma_buf_release+0x60/0x190 [ 339.617577] [] __fput+0x88/0x1d0 [ 339.617589] [] ____fput+0xc/0x18 [ 339.617607] [] task_work_run+0x9c/0xc0 [ 339.617622] [] do_notify_resume+0xfc/0x108 Fix this by referencing gntdev on each DMA buffer export and unreferencing on buffer release. Signed-off-by: Oleksandr Andrushchenko Reviewed-by: Boris Ostrovsky@oracle.com> Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin

pvcalls-front: fix potential null dereference

2019-02-27T09:08:56+00:00

[ Upstream commit b4711098066f1cf808d4dc11a1a842860a3292fe ] static checker warning: drivers/xen/pvcalls-front.c:373 alloc_active_ring() error: we previously assumed 'map->active.ring' could be null (see line 357) drivers/xen/pvcalls-front.c 351 static int alloc_active_ring(struct sock_mapping *map) 352 { 353 void *bytes; 354 355 map->active.ring = (struct pvcalls_data_intf *) 356 get_zeroed_page(GFP_KERNEL); 357 if (!map->active.ring) ^^^^^^^^^^^^^^^^^ Check 358 goto out; 359 360 map->active.ring->ring_order = PVCALLS_RING_ORDER; 361 bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 362 PVCALLS_RING_ORDER); 363 if (!bytes) 364 goto out; 365 366 map->active.data.in = bytes; 367 map->active.data.out = bytes + 368 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER); 369 370 return 0; 371 372 out: --> 373 free_active_ring(map); ^^^ Add null check on map->active.ring before dereferencing it to avoid any NULL pointer dereferences. Fixes: 9f51c05dc41a ("pvcalls-front: Avoid get_free_pages(GFP_KERNEL) under spinlock") Reported-by: Dan Carpenter Suggested-by: Boris Ostrovsky Signed-off-by: Wen Yang Reviewed-by: Boris Ostrovsky CC: Boris Ostrovsky CC: Juergen Gross CC: Stefano Stabellini CC: Dan Carpenter CC: xen-devel@lists.xenproject.org CC: linux-kernel@vger.kernel.org Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin