diff options
Diffstat (limited to 'pkg/sentry/mm/vma.go')
| -rw-r--r-- | pkg/sentry/mm/vma.go | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/pkg/sentry/mm/vma.go b/pkg/sentry/mm/vma.go index 28ba9f2f5..e9c9a80ea 100644 --- a/pkg/sentry/mm/vma.go +++ b/pkg/sentry/mm/vma.go @@ -84,6 +84,8 @@ func (mm *MemoryManager) createVMALocked(ctx context.Context, opts memmap.MMapOp // Inform the Mappable, if any, of the new mapping. if opts.Mappable != nil { + // The expression for writable is vma.canWriteMappableLocked(), but we + // don't yet have a vma. if err := opts.Mappable.AddMapping(ctx, mm, ar, opts.Offset, !opts.Private && opts.MaxPerms.Write); err != nil { return vmaIterator{}, usermem.AddrRange{}, err } @@ -366,7 +368,7 @@ func (mm *MemoryManager) removeVMAsLocked(ctx context.Context, ar usermem.AddrRa vmaAR := vseg.Range() vma := vseg.ValuePtr() if vma.mappable != nil { - vma.mappable.RemoveMapping(ctx, mm, vmaAR, vma.off, vma.isMappableAsWritable()) + vma.mappable.RemoveMapping(ctx, mm, vmaAR, vma.off, vma.canWriteMappableLocked()) } if vma.id != nil { vma.id.DecRef() @@ -381,6 +383,19 @@ func (mm *MemoryManager) removeVMAsLocked(ctx context.Context, ar usermem.AddrRa return vgap } +// canWriteMappableLocked returns true if it is possible for vma.mappable to be +// written to via this vma, i.e. if it is possible that +// vma.mappable.Translate(at.Write=true) may be called as a result of this vma. +// This includes via I/O with usermem.IOOpts.IgnorePermissions = true, such as +// PTRACE_POKEDATA. +// +// canWriteMappableLocked is equivalent to Linux's VM_SHARED. +// +// Preconditions: mm.mappingMu must be locked. +func (vma *vma) canWriteMappableLocked() bool { + return !vma.private && vma.maxPerms.Write +} + // vmaSetFunctions implements segment.Functions for vmaSet. type vmaSetFunctions struct{} |