From d9a3f5d0c7d675b3cb4519eccca341bac33456af Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Thu, 23 Jul 2020 18:46:10 -0700 Subject: Add permission checks to vfs2 truncate. - Check write permission on truncate(2). Unlike ftruncate(2), truncate(2) fails if the user does not have write permissions on the file. - For gofers under InteropModeShared, check file type before making a truncate request. We should fail early and avoid making an rpc when possible. Furthermore, depending on the remote host's failure may give us unexpected behavior--if the host converts the truncate request to an ftruncate syscall on an open fd, we will get EINVAL instead of EISDIR. Updates #2923. PiperOrigin-RevId: 322913569 --- pkg/sentry/syscalls/linux/vfs2/setstat.go | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'pkg/sentry/syscalls/linux') diff --git a/pkg/sentry/syscalls/linux/vfs2/setstat.go b/pkg/sentry/syscalls/linux/vfs2/setstat.go index 09ecfed26..6daedd173 100644 --- a/pkg/sentry/syscalls/linux/vfs2/setstat.go +++ b/pkg/sentry/syscalls/linux/vfs2/setstat.go @@ -178,6 +178,7 @@ func Truncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc Mask: linux.STATX_SIZE, Size: uint64(length), }, + NeedWritePerm: true, }) return 0, nil, handleSetSizeError(t, err) } @@ -197,6 +198,10 @@ func Ftruncate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys } defer file.DecRef() + if !file.IsWritable() { + return 0, nil, syserror.EINVAL + } + err := file.SetStat(t, vfs.SetStatOptions{ Stat: linux.Statx{ Mask: linux.STATX_SIZE, -- cgit v1.2.3