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The local task in process_vm_read|writev is just the calling task.

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We were using t.ThreadGroup.Leader() as the local task, which led to data races
reading fields that are owned by the task goroutine. But there's no need to use
the Leader, so we just use the calling task everywhere.

PiperOrigin-RevId: 570826256
This commit is contained in:
Nicolas Lacasse
2023-10-04 15:25:09 -07:00
committed by gVisor bot
parent cf93d15690
commit c39ecc4eb4
1 changed files with 8 additions and 13 deletions
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pkg/sentry/syscalls/linux/sys_process_vm.go
+8 -13
View File
@@ -65,15 +65,10 @@ func processVMOp(t *kernel.Task, args arch.SyscallArguments, op processVMOpType)
return 0, nil, linuxerr.EFAULT
}
// Determine local and remote processes.
// Local process is always the caller.
localTask := t.ThreadGroup().Leader()
if localTask == nil {
return 0, nil, linuxerr.ESRCH
}
// Remote process is the pid specified in the syscall arguments. It is
// allowed to be the same as the caller process.
remoteThreadGroup := localTask.PIDNamespace().ThreadGroupWithID(pid)
// Local process is always the current task (t). Remote process is the
// pid specified in the syscall arguments. It is allowed to be the same
// as the caller process.
remoteThreadGroup := t.PIDNamespace().ThreadGroupWithID(pid)
if remoteThreadGroup == nil {
return 0, nil, linuxerr.ESRCH
}
@@ -85,7 +80,7 @@ func processVMOp(t *kernel.Task, args arch.SyscallArguments, op processVMOpType)
// man 2 process_vm_read: "Permission to read from or write to another
// process is governed by a ptrace access mode
// PTRACE_MODE_ATTACH_REALCREDS check; see ptrace(2)."
if !localTask.CanTrace(remoteTask, true /* attach */) {
if !t.CanTrace(remoteTask, true /* attach */) {
return 0, nil, linuxerr.EPERM
}
@@ -99,14 +94,14 @@ func processVMOp(t *kernel.Task, args arch.SyscallArguments, op processVMOpType)
readCtx: remoteTask.CopyContext(t, usermem.IOOpts{}),
readAddr: rvec,
readIovecCount: riovcnt,
writeCtx: localTask.CopyContext(t, usermem.IOOpts{AddressSpaceActive: true}),
writeCtx: t.CopyContext(t, usermem.IOOpts{AddressSpaceActive: true}),
writeAddr: lvec,
writeIovecCount: liovcnt,
}
case processVMOpWrite:
// Read from local process and write into remote.
opArgs = processVMOpArgs{
readCtx: localTask.CopyContext(t, usermem.IOOpts{AddressSpaceActive: true}),
readCtx: t.CopyContext(t, usermem.IOOpts{AddressSpaceActive: true}),
readAddr: lvec,
readIovecCount: liovcnt,
writeCtx: remoteTask.CopyContext(t, usermem.IOOpts{}),
@@ -121,7 +116,7 @@ func processVMOp(t *kernel.Task, args arch.SyscallArguments, op processVMOpType)
n int
err error
)
if localTask == remoteTask {
if t == remoteTask {
// No need to lock remote process's task mutex since it is the
// same as this process.
n, err = doProcessVMOpMaybeLocked(t, opArgs)