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=== Description (from pull-request) ===
Ensure that we don't cross a page boundary.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
From ae1d7737d49b1169d54de72c7e63810a77c260af Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brau...@ubuntu.com>
Date: Tue, 28 Jul 2020 13:53:38 +0200
Subject: [PATCH] seccomp: switch from individual pread() to process_vm_readv()
Ensure that we don't cross a page boundary.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
---
lxd/seccomp/seccomp.go | 116 +++++++++++++++++++++++++----------------
1 file changed, 70 insertions(+), 46 deletions(-)
diff --git a/lxd/seccomp/seccomp.go b/lxd/seccomp/seccomp.go
index 404b4998e5..c08c9ed133 100644
--- a/lxd/seccomp/seccomp.go
+++ b/lxd/seccomp/seccomp.go
@@ -1410,64 +1410,79 @@ func (s *Server) HandleMountSyscall(c Instance, siov
*Iovec) int {
defer pidFd.Close()
}
- // const char *source
- args.source = ""
+ buf1 := [4096]C.char{}
+ buf2 := [4096]C.char{}
+ buf3 := [4096]C.char{}
+ buf4 := [4096]C.char{}
+
+ // process_vm_readv() doesn't like crossing page boundaries when
+ // reading individual syscall args.
+ bufSize := uint64(4096)
+ if bufSize > pageSize {
+ bufSize = pageSize
+ }
+
+ mntSource := buf1[:bufSize]
+ mntTarget := buf2[:bufSize]
+ mntFs := buf3[:bufSize]
+ mntData := buf4[:bufSize]
+
+ localIov := []unix.Iovec{
+ unix.Iovec{Base: (*byte)(unsafe.Pointer(&mntSource[0]))},
+ unix.Iovec{Base: (*byte)(unsafe.Pointer(&mntTarget[0]))},
+ unix.Iovec{Base: (*byte)(unsafe.Pointer(&mntFs[0]))},
+ unix.Iovec{Base: (*byte)(unsafe.Pointer(&mntData[0]))},
+ }
+
+ remoteIov := []unix.RemoteIovec{
+ unix.RemoteIovec{Base: uintptr(siov.req.data.args[0])},
+ unix.RemoteIovec{Base: uintptr(siov.req.data.args[1])},
+ unix.RemoteIovec{Base: uintptr(siov.req.data.args[2])},
+ unix.RemoteIovec{Base: uintptr(siov.req.data.args[4])},
+ }
+
if siov.req.data.args[0] != 0 {
- cBuf := [unix.PathMax]C.char{}
- _, err := C.pread(C.int(siov.memFd), unsafe.Pointer(&cBuf[0]),
C.size_t(unix.PathMax), C.off_t(siov.req.data.args[0]))
- if err != nil {
- ctx["err"] = fmt.Sprintf("Failed to read memory for
first argument of mount syscall: %s", err)
- ctx["syscall_continue"] = "true"
- C.seccomp_notify_update_response(siov.resp, 0,
C.uint32_t(seccompUserNotifFlagContinue))
- return 0
- }
- args.source = C.GoString(&cBuf[0])
+ localIov[0].Len = bufSize
+ remoteIov[0].Len = int(bufSize)
}
- // const char *target
- args.target = ""
if siov.req.data.args[1] != 0 {
- cBuf := [unix.PathMax]C.char{}
- _, err := C.pread(C.int(siov.memFd), unsafe.Pointer(&cBuf[0]),
C.size_t(unix.PathMax), C.off_t(siov.req.data.args[1]))
- if err != nil {
- ctx["err"] = fmt.Sprintf("Failed to read memory for
second argument of mount syscall: %s", err)
- ctx["syscall_continue"] = "true"
- C.seccomp_notify_update_response(siov.resp, 0,
C.uint32_t(seccompUserNotifFlagContinue))
- return 0
- }
- args.target = C.GoString(&cBuf[0])
+ localIov[1].Len = bufSize
+ remoteIov[1].Len = int(bufSize)
}
- // const char *filesystemtype
- args.fstype = ""
if siov.req.data.args[2] != 0 {
- cBuf := [unix.PathMax]C.char{}
- _, err := C.pread(C.int(siov.memFd), unsafe.Pointer(&cBuf[0]),
C.size_t(unix.PathMax), C.off_t(siov.req.data.args[2]))
- if err != nil {
- ctx["err"] = fmt.Sprintf("Failed to read memory for
third argument of mount syscall: %s", err)
- ctx["syscall_continue"] = "true"
- C.seccomp_notify_update_response(siov.resp, 0,
C.uint32_t(seccompUserNotifFlagContinue))
- return 0
- }
- args.fstype = C.GoString(&cBuf[0])
+ localIov[2].Len = bufSize
+ remoteIov[2].Len = int(bufSize)
+ }
+
+ if siov.req.data.args[4] != 0 {
+ localIov[3].Len = bufSize
+ remoteIov[3].Len = int(bufSize)
}
+ _, err := unix.ProcessVMReadv(args.pid, localIov, remoteIov, 0)
+ if err != nil {
+ ctx["err"] = fmt.Sprintf("Failed to read process memory of
mount syscall: %s", err)
+ ctx["syscall_continue"] = "true"
+ C.seccomp_notify_update_response(siov.resp, 0,
C.uint32_t(seccompUserNotifFlagContinue))
+ return 0
+ }
+
+ // const char *source
+ args.source = C.GoString(&mntSource[0])
+ ctx["source"] = args.source
+ // const char *target
+ args.target = C.GoString(&mntTarget[0])
+ ctx["target"] = args.target
+ // const char *filesystemtype
+ args.fstype = C.GoString(&mntFs[0])
+ ctx["fstype"] = args.fstype
// unsigned long mountflags
args.flags = int(siov.req.data.args[3])
-
// const void *data
- args.data = ""
- if siov.req.data.args[4] != 0 {
- cBuf := [unix.PathMax]C.char{}
- _, err := C.pread(C.int(siov.memFd), unsafe.Pointer(&cBuf[0]),
C.size_t(unix.PathMax), C.off_t(siov.req.data.args[4]))
- if err != nil {
- ctx["err"] = fmt.Sprintf("Failed to read memory for
fifth argument of mount syscall: %s", err)
- ctx["syscall_continue"] = "true"
- C.seccomp_notify_update_response(siov.resp, 0,
C.uint32_t(seccompUserNotifFlagContinue))
- return 0
- }
- args.data = C.GoString(&cBuf[0])
- }
+ args.data = C.GoString(&mntData[0])
+ ctx["data"] = args.data
ok, fuseBinary := s.MountSyscallValid(c, &args)
if !ok {
@@ -1745,3 +1760,12 @@ func (s *Server) MountSyscallShift(c Instance) bool {
return false
}
+
+var pageSize uint64 = 4096
+
+func init() {
+ tmp := unix.Getpagesize()
+ if tmp > 0 {
+ pageSize = uint64(tmp)
+ }
+}
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