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-rw-r--r--pkg/sentry/kernel/fd_table.go6
1 files changed, 4 insertions, 2 deletions
diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
index 1f3a57dc1..cc3f43a45 100644
--- a/pkg/sentry/kernel/fd_table.go
+++ b/pkg/sentry/kernel/fd_table.go
@@ -81,7 +81,9 @@ type FDTable struct {
// mu protects below.
mu sync.Mutex `state:"nosave"`
- // used contains the number of non-nil entries.
+ // used contains the number of non-nil entries. It must be accessed
+ // atomically. It may be read atomically without holding mu (but not
+ // written).
used int32
// descriptorTable holds descriptors.
@@ -317,7 +319,7 @@ func (f *FDTable) Get(fd int32) (*fs.File, FDFlags) {
// GetFDs returns a list of valid fds.
func (f *FDTable) GetFDs() []int32 {
- fds := make([]int32, 0, f.used)
+ fds := make([]int32, 0, int(atomic.LoadInt32(&f.used)))
f.forEach(func(fd int32, file *fs.File, flags FDFlags) {
fds = append(fds, fd)
})