linux-stable.git/drivers/xen/gntdev.c, branch linux-5.4.y

xen/gntdev: Prevent leaking grants

2022-11-03T14:56:54+00:00

commit 0991028cd49567d7016d1b224fe0117c35059f86 upstream.

Prior to this commit, if a grant mapping operation failed partially,
some of the entries in the map_ops array would be invalid, whereas all
of the entries in the kmap_ops array would be valid. This in turn would
cause the following logic in gntdev_map_grant_pages to become invalid:

  for (i = 0; i < map->count; i++) {
    if (map->map_ops[i].status == GNTST_okay) {
      map->unmap_ops[i].handle = map->map_ops[i].handle;
      if (!use_ptemod)
        alloced++;
    }
    if (use_ptemod) {
      if (map->kmap_ops[i].status == GNTST_okay) {
        if (map->map_ops[i].status == GNTST_okay)
          alloced++;
        map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
      }
    }
  }
  ...
  atomic_add(alloced, &map->live_grants);

Assume that use_ptemod is true (i.e., the domain mapping the granted
pages is a paravirtualized domain). In the code excerpt above, note that
the "alloced" variable is only incremented when both kmap_ops[i].status
and map_ops[i].status are set to GNTST_okay (i.e., both mapping
operations are successful).  However, as also noted above, there are
cases where a grant mapping operation fails partially, breaking the
assumption of the code excerpt above.

The aforementioned causes map->live_grants to be incorrectly set. In
some cases, all of the map_ops mappings fail, but all of the kmap_ops
mappings succeed, meaning that live_grants may remain zero. This in turn
makes it impossible to unmap the successfully grant-mapped pages pointed
to by kmap_ops, because unmap_grant_pages has the following snippet of
code at its beginning:

  if (atomic_read(&map->live_grants) == 0)
    return; /* Nothing to do */

In other cases where only some of the map_ops mappings fail but all
kmap_ops mappings succeed, live_grants is made positive, but when the
user requests unmapping the grant-mapped pages, __unmap_grant_pages_done
will then make map->live_grants negative, because the latter function
does not check if all of the pages that were requested to be unmapped
were actually unmapped, and the same function unconditionally subtracts
"data->count" (i.e., a value that can be greater than map->live_grants)
from map->live_grants. The side effects of a negative live_grants value
have not been studied.

The net effect of all of this is that grant references are leaked in one
of the above conditions. In Qubes OS v4.1 (which uses Xen's grant
mechanism extensively for X11 GUI isolation), this issue manifests
itself with warning messages like the following to be printed out by the
Linux kernel in the VM that had granted pages (that contain X11 GUI
window data) to dom0: "g.e. 0x1234 still pending", especially after the
user rapidly resizes GUI VM windows (causing some grant-mapping
operations to partially or completely fail, due to the fact that the VM
unshares some of the pages as part of the window resizing, making the
pages impossible to grant-map from dom0).

The fix for this issue involves counting all successful map_ops and
kmap_ops mappings separately, and then adding the sum to live_grants.
During unmapping, only the number of successfully unmapped grants is
subtracted from live_grants. The code is also modified to check for
negative live_grants values after the subtraction and warn the user.

Link: https://github.com/QubesOS/qubes-issues/issues/7631
Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
Cc: stable@vger.kernel.org
Signed-off-by: M. Vefa Bicakci 
Acked-by: Demi Marie Obenour 
Reviewed-by: Juergen Gross 
Link: https://lore.kernel.org/r/20221002222006.2077-2-m.v.b@runbox.com
Signed-off-by: Juergen Gross 
Signed-off-by: Demi Marie Obenour 
Signed-off-by: Greg Kroah-Hartman

Xen/gntdev: don't ignore kernel unmapping error

2022-11-03T14:56:54+00:00

commit f28347cc66395e96712f5c2db0a302ee75bafce6 upstream.

While working on XSA-361 and its follow-ups, I failed to spot another
place where the kernel mapping part of an operation was not treated the
same as the user space part. Detect and propagate errors and add a 2nd
pr_debug().

Signed-off-by: Jan Beulich 
Reviewed-by: Juergen Gross 
Link: https://lore.kernel.org/r/c2513395-74dc-aea3-9192-fd265aa44e35@suse.com
Signed-off-by: Juergen Gross 
Signed-off-by: Demi Marie Obenour 
Co-authored-by: Demi Marie Obenour 
Signed-off-by: Greg Kroah-Hartman

xen/gntdev: Ignore failure to unmap INVALID_GRANT_HANDLE

2022-07-29T15:14:09+00:00

commit 166d3863231667c4f64dee72b77d1102cdfad11f upstream.

The error paths of gntdev_mmap() can call unmap_grant_pages() even
though not all of the pages have been successfully mapped.  This will
trigger the WARN_ON()s in __unmap_grant_pages_done().  The number of
warnings can be very large; I have observed thousands of lines of
warnings in the systemd journal.

Avoid this problem by only warning on unmapping failure if the handle
being unmapped is not INVALID_GRANT_HANDLE.  The handle field of any
page that was not successfully mapped will be INVALID_GRANT_HANDLE, so
this catches all cases where unmapping can legitimately fail.

Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
Cc: stable@vger.kernel.org
Suggested-by: Juergen Gross 
Signed-off-by: Demi Marie Obenour 
Reviewed-by: Oleksandr Tyshchenko 
Reviewed-by: Juergen Gross 
Link: https://lore.kernel.org/r/20220710230522.1563-1-demi@invisiblethingslab.com
Signed-off-by: Juergen Gross 
Signed-off-by: Greg Kroah-Hartman

xen/gntdev: Avoid blocking in unmap_grant_pages()

2022-07-07T15:36:50+00:00

commit dbe97cff7dd9f0f75c524afdd55ad46be3d15295 upstream.

unmap_grant_pages() currently waits for the pages to no longer be used.
In https://github.com/QubesOS/qubes-issues/issues/7481, this lead to a
deadlock against i915: i915 was waiting for gntdev's MMU notifier to
finish, while gntdev was waiting for i915 to free its pages.  I also
believe this is responsible for various deadlocks I have experienced in
the past.

Avoid these problems by making unmap_grant_pages async.  This requires
making it return void, as any errors will not be available when the
function returns.  Fortunately, the only use of the return value is a
WARN_ON(), which can be replaced by a WARN_ON when the error is
detected.  Additionally, a failed call will not prevent further calls
from being made, but this is harmless.

Because unmap_grant_pages is now async, the grant handle will be sent to
INVALID_GRANT_HANDLE too late to prevent multiple unmaps of the same
handle.  Instead, a separate bool array is allocated for this purpose.
This wastes memory, but stuffing this information in padding bytes is
too fragile.  Furthermore, it is necessary to grab a reference to the
map before making the asynchronous call, and release the reference when
the call returns.

It is also necessary to guard against reentrancy in gntdev_map_put(),
and to handle the case where userspace tries to map a mapping whose
contents have not all been freed yet.

Fixes: 745282256c75 ("xen/gntdev: safely unmap grants in case they are still in use")
Cc: stable@vger.kernel.org
Signed-off-by: Demi Marie Obenour 
Reviewed-by: Juergen Gross 
Link: https://lore.kernel.org/r/20220622022726.2538-1-demi@invisiblethingslab.com
Signed-off-by: Juergen Gross 
Signed-off-by: Greg Kroah-Hartman

Xen/gntdev: correct error checking in gntdev_map_grant_pages()

2021-02-23T14:02:26+00:00

commit ebee0eab08594b2bd5db716288a4f1ae5936e9bc upstream.

Failure of the kernel part of the mapping operation should also be
indicated as an error to the caller, or else it may assume the
respective kernel VA is okay to access.

Furthermore gnttab_map_refs() failing still requires recording
successfully mapped handles, so they can be unmapped subsequently. This
in turn requires there to be a way to tell full hypercall failure from
partial success - preset map_op status fields such that they won't
"happen" to look as if the operation succeeded.

Also again use GNTST_okay instead of implying its value (zero).

This is part of XSA-361.

Signed-off-by: Jan Beulich 
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross 
Signed-off-by: Juergen Gross 
Signed-off-by: Greg Kroah-Hartman

Xen/gntdev: correct dev_bus_addr handling in gntdev_map_grant_pages()

2021-02-23T14:02:26+00:00

commit dbe5283605b3bc12ca45def09cc721a0a5c853a2 upstream.

We may not skip setting the field in the unmap structure when
GNTMAP_device_map is in use - such an unmap would fail to release the
respective resources (a page ref in the hypervisor). Otoh the field
doesn't need setting at all when GNTMAP_device_map is not in use.

To record the value for unmapping, we also better don't use our local
p2m: In particular after a subsequent change it may not have got updated
for all the batch elements. Instead it can simply be taken from the
respective map's results.

We can additionally avoid playing this game altogether for the kernel
part of the mappings in (x86) PV mode.

This is part of XSA-361.

Signed-off-by: Jan Beulich 
Cc: stable@vger.kernel.org
Reviewed-by: Stefano Stabellini 
Signed-off-by: Juergen Gross 
Signed-off-by: Greg Kroah-Hartman

xen/gntdev.c: Mark pages as dirty

2020-11-01T11:01:06+00:00

commit 779055842da5b2e508f3ccf9a8153cb1f704f566 upstream.

There seems to be a bug in the original code when gntdev_get_page()
is called with writeable=true then the page needs to be marked dirty
before being put.

To address this, a bool writeable is added in gnt_dev_copy_batch, set
it in gntdev_grant_copy_seg() (and drop `writeable` argument to
gntdev_get_page()) and then, based on batch->writeable, use
set_page_dirty_lock().

Fixes: a4cdb556cae0 (xen/gntdev: add ioctl for grant copy)
Suggested-by: Boris Ostrovsky 
Signed-off-by: Souptick Joarder 
Cc: John Hubbard 
Cc: Boris Ostrovsky 
Cc: Juergen Gross 
Cc: David Vrabel 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1599375114-32360-1-git-send-email-jrdr.linux@gmail.com
Reviewed-by: Boris Ostrovsky 
Signed-off-by: Boris Ostrovsky 
Signed-off-by: Greg Kroah-Hartman

xen: Stop abusing DT of_dma_configure API

2019-10-10T15:43:35+00:00

As the removed comments say, these aren't DT based devices.
of_dma_configure() is going to stop allowing a NULL DT node and calling
it will no longer work.

The comment is also now out of date as of commit 9ab91e7c5c51 ("arm64:
default to the direct mapping in get_arch_dma_ops"). Direct mapping
is now the default rather than dma_dummy_ops.

According to Stefano and Oleksandr, the only other part needed is
setting the DMA masks and there's no reason to restrict the masks to
32-bits. So set the masks to 64 bits.

Cc: Robin Murphy 
Cc: Julien Grall 
Cc: Nicolas Saenz Julienne 
Cc: Oleksandr Andrushchenko 
Cc: Boris Ostrovsky 
Cc: Juergen Gross 
Cc: Stefano Stabellini 
Cc: Christoph Hellwig 
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Rob Herring 
Acked-by: Oleksandr Andrushchenko 
Reviewed-by: Boris Ostrovsky 
Signed-off-by: Boris Ostrovsky

xen/gntdev.c: Replace vm_map_pages() with vm_map_pages_zero()

2019-07-31T06:13:59+00:00

'commit df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()")'
breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages()
will:
 - use map->pages starting at vma->vm_pgoff instead of 0
 - verify map->count against vma_pages()+vma->vm_pgoff instead of just
   vma_pages().

In practice, this breaks using a single gntdev FD for mapping multiple
grants.

relevant strace output:
[pid   857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0
[pid   857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7, 0) =
0x777f1211b000
[pid   857] ioctl(7, IOCTL_GNTDEV_SET_UNMAP_NOTIFY, 0x7ffd3407b710) = 0
[pid   857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0
[pid   857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7,
0x1000) = -1 ENXIO (No such device or address)

details here:
https://github.com/QubesOS/qubes-issues/issues/5199

The reason is -> ( copying Marek's word from discussion)

vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's
basically using this parameter for "which grant reference to map".
map struct returned by gntdev_find_map_index() describes just the pages
to be mapped. Specifically map->pages[0] should be mapped at
vma->vm_start, not vma->vm_start+vma->vm_pgoff*PAGE_SIZE.

When trying to map grant with index (aka vma->vm_pgoff) > 1,
__vm_map_pages() will refuse to map it because it will expect map->count
to be at least vma_pages(vma)+vma->vm_pgoff, while it is exactly
vma_pages(vma).

Converting vm_map_pages() to use vm_map_pages_zero() will fix the
problem.

Marek has tested and confirmed the same.

Cc: stable@vger.kernel.org # v5.2+
Fixes: df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()")

Reported-by: Marek Marczykowski-Górecki 
Signed-off-by: Souptick Joarder 
Tested-by: Marek Marczykowski-Górecki 
Reviewed-by: Boris Ostrovsky 
Signed-off-by: Juergen Gross

mm/pgtable: drop pgtable_t variable from pte_fn_t functions

2019-07-12T18:05:46+00:00

Drop the pgtable_t variable from all implementation for pte_fn_t as none
of them use it.  apply_to_pte_range() should stop computing it as well.
Should help us save some cycles.

Link: http://lkml.kernel.org/r/1556803126-26596-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual 
Acked-by: Matthew Wilcox 
Cc: Ard Biesheuvel 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Michal Hocko 
Cc: Logan Gunthorpe 
Cc: "Kirill A. Shutemov" 
Cc: Dan Williams 
Cc: 
Cc: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds