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Restrict the UVM ioctl operations to the owner process when UVM_INIT_FLAGS_MULTI_PROCESS_SHARING_MODE is not set by the application. #12721

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Restrict the UVM ioctl operations to the owner process when UVM_INIT_FLAGS_MULTI_PROCESS_SHARING_MODE is not set by the application. #12721

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23 changes: 23 additions & 0 deletions pkg/sentry/devices/nvproxy/uvm.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ package nvproxy

import (
"fmt"
"sync"

"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/nvgpu"
Expand Down Expand Up @@ -81,6 +82,13 @@ type uvmFD struct {
memmapFile uvmFDMemmapFile

queue waiter.Queue

// mu protects fields below.
mu sync.Mutex
// multiProcessSharing is true if the FD was initialized with
// UVM_INIT_FLAGS_MULTI_PROCESS_SHARING_MODE.
multiProcessSharing bool
ownerTG *kernel.ThreadGroup
}

// Release implements vfs.FileDescriptionImpl.Release.
Expand Down Expand Up @@ -132,6 +140,16 @@ func (fd *uvmFD) Ioctl(ctx context.Context, uio usermem.IO, sysno uintptr, args
ctx.Debugf("nvproxy: uvm ioctl %d = %#x", cmd, cmd)
}

// Enforce process isolation: If the FD was initialized without multi-process
// sharing, only the original ThreadGroup can use it.
fd.mu.Lock()
if fd.ownerTG != nil && !fd.multiProcessSharing && t.ThreadGroup() != fd.ownerTG {
fd.mu.Unlock()
ctx.Warningf("nvproxy: blocked cross-process uvm ioctl %d (sharing mode disabled)", cmd)
return 0, linuxerr.EACCES
}
fd.mu.Unlock()

ui := uvmIoctlState{
fd: fd,
ctx: ctx,
Expand Down Expand Up @@ -191,6 +209,11 @@ func uvmInitialize(ui *uvmIoctlState) (uintptr, error) {
return 0, err
}
origFlags := ioctlParams.Flags
// Record the original intent and owner
ui.fd.mu.Lock()
ui.fd.multiProcessSharing = (origFlags & nvgpu.UVM_INIT_FLAGS_MULTI_PROCESS_SHARING_MODE) != 0
ui.fd.ownerTG = ui.t.ThreadGroup()
ui.fd.mu.Unlock()
// This is necessary to share the host UVM FD between sentry and
// application processes.
ioctlParams.Flags = ioctlParams.Flags | nvgpu.UVM_INIT_FLAGS_MULTI_PROCESS_SHARING_MODE
Expand Down
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