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fasync: Unlock the FileAsync mutex before sending signal

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This cl reverts cl/537942317 and cl/538645255. We need to lock the mutex once
and read all required fields of the FileAsync structure and then release it
right before calling SendSignal.

Right now, getPermAndSignal() and recipient() can return inconsistent results,
because FileAsync can be changed between them.

PiperOrigin-RevId: 538829847
This commit is contained in:
Andrei Vagin
2023-06-08 10:49:08 -07:00
committed by gVisor bot
parent cc39ca2398
commit 7a92412c08
1 changed files with 18 additions and 28 deletions
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pkg/sentry/kernel/fasync/fasync.go
+18 -28
View File
@@ -85,12 +85,17 @@ type FileAsync struct {
recipientT *kernel.Task
}
func (a *FileAsync) recipient() *kernel.Task {
// NotifyEvent implements waiter.EventListener.NotifyEvent.
func (a *FileAsync) NotifyEvent(mask waiter.EventMask) {
a.mu.Lock()
defer a.mu.Unlock()
locked := true
defer func() {
if locked {
a.mu.Unlock()
}
}()
if !a.registered {
// No recipient has been registered.
return nil
return
}
t := a.recipientT
tg := a.recipientTG
@@ -100,34 +105,17 @@ func (a *FileAsync) recipient() *kernel.Task {
if tg != nil {
t = tg.Leader()
}
return t
}
// getPermAndSignal checks the credentials and returns the result of the
// credentials check and signal.
//
//go:nosplit
func (a *FileAsync) getPermAndSignal(c *auth.Credentials) (int32, bool) {
a.mu.Lock()
defer a.mu.Unlock()
sig := int32(a.signal)
if t == nil {
// No recipient has been registered.
return
}
c := t.Credentials()
// Logic from sigio_perm in fs/fcntl.c.
permCheck := (a.requester.EffectiveKUID == 0 ||
a.requester.EffectiveKUID == c.SavedKUID ||
a.requester.EffectiveKUID == c.RealKUID ||
a.requester.RealKUID == c.SavedKUID ||
a.requester.RealKUID == c.RealKUID)
return sig, permCheck
}
// NotifyEvent implements waiter.EventListener.NotifyEvent.
func (a *FileAsync) NotifyEvent(mask waiter.EventMask) {
t := a.recipient()
if t == nil {
return
}
c := t.Credentials()
sig, permCheck := a.getPermAndSignal(c)
if !permCheck {
return
}
@@ -135,8 +123,8 @@ func (a *FileAsync) NotifyEvent(mask waiter.EventMask) {
Signo: int32(linux.SIGIO),
Code: linux.SI_KERNEL,
}
if sig != 0 {
signalInfo.Signo = sig
if a.signal != 0 {
signalInfo.Signo = int32(a.signal)
signalInfo.SetFD(uint32(a.fd))
var band int64
for m, bandCode := range bandTable {
@@ -146,6 +134,8 @@ func (a *FileAsync) NotifyEvent(mask waiter.EventMask) {
}
signalInfo.SetBand(band)
}
a.mu.Unlock()
locked = false
t.SendSignal(signalInfo)
}