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vmm: Prevent memory overcommitment through virtio-fs shared regions

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When a virtio-fs device is created with a dedicated shared region, by
default the region should be mapped as PROT_NONE so that no pages can be
faulted in.

It's only when the guest performs the mount of the virtiofs filesystem
that we can expect the VMM, on behalf of the backend, to perform some
new mappings in the reserved shared window, using PROT_READ and/or
PROT_WRITE.

Fixes #763

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
(cherry picked from commit 3edc2bd6ab33299b88c9cf6ed6ca50292ec3fea5)
This commit is contained in:
Sebastien Boeuf 2020-02-17 10:38:39 +01:00 committed by Rob Bradford
parent 3534540e6b
commit 9c3166237d
1 changed files with 7 additions and 2 deletions
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9
vmm/src/device_manager.rs
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@ -1028,8 +1028,13 @@ impl DeviceManager {
)
.ok_or(DeviceManagerError::FsRangeAllocation)?;
let mmap_region = MmapRegion::new(fs_cache as usize)
.map_err(DeviceManagerError::NewMmapRegion)?;
let mmap_region = MmapRegion::build(
None,
fs_cache as usize,
libc::PROT_NONE,
libc::MAP_ANONYMOUS | libc::MAP_PRIVATE,
)
.map_err(DeviceManagerError::NewMmapRegion)?;
let addr: u64 = mmap_region.as_ptr() as u64;
self._mmap_regions.push(mmap_region);