Cygwin: fhandler_pipe: fix permission problem
The read handles of pipes created by CreateNamedPipe don't have FILE_WRITE_ATTRIBUTES access unless the pipe is created with PIPE_ACCESS_DUPLEX. This causes set_pipe_non_blocking to fail on such handles. To fix this, add a helper function nt_create, which uses NtCreateNamedPipeFile instead of CreateNamedPipe and gives us more flexibility in setting access rights. Use this helper function in fhandler_pipe::create (fhandler_pipe *[2], unsigned, int), which is the version of fhandler_pipe::create used by the pipe and pipe2 system calls. For convenience, also add a static member function fhandler_pipe::npfs_handle similar to those used by fhandler_fifo and fhandler_socket_unix.
This commit is contained in:
Ken Brown
Corinna Vinschen
parent
d0ad52aa6e
commit
f56206cd86
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@ -1267,6 +1267,7 @@ public:
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int __reg3 fadvise (off_t, off_t, int);
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int __reg3 ftruncate (off_t, bool);
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int init (HANDLE, DWORD, mode_t, int64_t);
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static NTSTATUS npfs_handle (HANDLE &);
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static int create (fhandler_pipe *[2], unsigned, int);
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static DWORD create (LPSECURITY_ATTRIBUTES, HANDLE *, HANDLE *, DWORD,
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const char *, DWORD, int64_t *unique_id = NULL);
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@ -35,7 +35,12 @@ fhandler_pipe::fhandler_pipe ()
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need_fork_fixup (true);
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}
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/* This also sets the pipe's read mode to byte_stream unconditionally. */
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/* The following function is intended for fhandler_pipe objects
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created by the second version of fhandler_pipe::create below. See
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the comment preceding the latter.
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In addition to setting the blocking mode of the pipe handle, it
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also sets the pipe's read mode to byte_stream unconditionally. */
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void
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fhandler_pipe::set_pipe_non_blocking (bool nonblocking)
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{
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@ -566,6 +571,24 @@ fhandler_pipe::create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
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return 0;
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}
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/* The next version of fhandler_pipe::create used to call the previous
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version. But the read handle created by the latter doesn't have
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FILE_WRITE_ATTRIBUTES access unless the pipe is created with
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PIPE_ACCESS_DUPLEX, and it doesn't seem possible to add that access
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right. This causes set_pipe_non_blocking to fail.
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To fix this we will define a helper function 'nt_create' that is
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similar to the above fhandler_pipe::create but uses
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NtCreateNamedPipeFile instead of CreateNamedPipe; this gives more
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flexibility in setting the access rights. We will use this helper
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function in the version of fhandler_pipe::create below, which
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suffices for all of our uses of set_pipe_non_blocking. For
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simplicity, nt_create will omit the 'open_mode' and 'name'
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parameters, which aren't needed for our purposes. */
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static int nt_create (LPSECURITY_ATTRIBUTES, PHANDLE, PHANDLE, DWORD,
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int64_t *);
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int
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fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
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{
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@ -574,7 +597,7 @@ fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
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int res = -1;
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int64_t unique_id;
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int ret = create (sa, &r, &w, psize, NULL, 0, &unique_id);
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int ret = nt_create (sa, &r, &w, psize, &unique_id);
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if (ret)
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__seterrno_from_win_error (ret);
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else if ((fhs[0] = (fhandler_pipe *) build_fh_dev (*piper_dev)) == NULL)
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@ -601,6 +624,168 @@ fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
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return res;
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}
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NTSTATUS
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fhandler_pipe::npfs_handle (HANDLE &nph)
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{
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static NO_COPY SRWLOCK npfs_lock;
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static NO_COPY HANDLE npfs_dirh;
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NTSTATUS status = STATUS_SUCCESS;
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OBJECT_ATTRIBUTES attr;
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IO_STATUS_BLOCK io;
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/* Lockless after first call. */
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if (npfs_dirh)
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{
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nph = npfs_dirh;
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return STATUS_SUCCESS;
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}
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AcquireSRWLockExclusive (&npfs_lock);
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if (!npfs_dirh)
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{
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InitializeObjectAttributes (&attr, &ro_u_npfs, 0, NULL, NULL);
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status = NtOpenFile (&npfs_dirh, FILE_READ_ATTRIBUTES | SYNCHRONIZE,
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&attr, &io, FILE_SHARE_READ | FILE_SHARE_WRITE,
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0);
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}
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ReleaseSRWLockExclusive (&npfs_lock);
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if (NT_SUCCESS (status))
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nph = npfs_dirh;
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return status;
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}
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static int
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nt_create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
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DWORD psize, int64_t *unique_id)
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{
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NTSTATUS status;
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HANDLE npfsh;
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ACCESS_MASK access;
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OBJECT_ATTRIBUTES attr;
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IO_STATUS_BLOCK io;
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LARGE_INTEGER timeout;
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/* Default to error. */
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if (r)
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*r = NULL;
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if (w)
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*w = NULL;
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status = fhandler_pipe::npfs_handle (npfsh);
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if (!NT_SUCCESS (status))
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{
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__seterrno_from_nt_status (status);
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return GetLastError ();
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}
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/* Ensure that there is enough pipe buffer space for atomic writes. */
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if (!psize)
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psize = DEFAULT_PIPEBUFSIZE;
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UNICODE_STRING pipename;
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WCHAR pipename_buf[MAX_PATH];
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size_t len = __small_swprintf (pipename_buf, L"%S-%u-",
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&cygheap->installation_key,
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GetCurrentProcessId ());
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access = GENERIC_READ | FILE_WRITE_ATTRIBUTES;
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ULONG pipe_type = pipe_byte ? FILE_PIPE_BYTE_STREAM_TYPE
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: FILE_PIPE_MESSAGE_TYPE;
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/* Retry NtCreateNamedPipeFile as long as the pipe name is in use.
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Retrying will probably never be necessary, but we want
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to be as robust as possible. */
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DWORD err = 0;
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while (r && !*r)
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{
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static volatile ULONG pipe_unique_id;
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LONG id = InterlockedIncrement ((LONG *) &pipe_unique_id);
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__small_swprintf (pipename_buf + len, L"pipe-nt-%p", id);
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if (unique_id)
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*unique_id = ((int64_t) id << 32 | GetCurrentProcessId ());
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debug_printf ("name %W, size %u, mode %s", pipename_buf, psize,
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(pipe_type & FILE_PIPE_MESSAGE_TYPE)
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? "PIPE_TYPE_MESSAGE" : "PIPE_TYPE_BYTE");
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RtlInitUnicodeString (&pipename, pipename_buf);
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InitializeObjectAttributes (&attr, &pipename,
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sa_ptr->bInheritHandle ? OBJ_INHERIT : 0,
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npfsh, sa_ptr->lpSecurityDescriptor);
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timeout.QuadPart = -500000;
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status = NtCreateNamedPipeFile (r, access, &attr, &io,
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FILE_SHARE_READ | FILE_SHARE_WRITE,
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FILE_CREATE, 0, pipe_type,
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FILE_PIPE_BYTE_STREAM_MODE,
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0, 1, psize, psize, &timeout);
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if (NT_SUCCESS (status))
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{
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debug_printf ("pipe read handle %p", *r);
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err = 0;
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break;
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}
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switch (status)
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{
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case STATUS_PIPE_BUSY:
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case STATUS_INSTANCE_NOT_AVAILABLE:
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case STATUS_PIPE_NOT_AVAILABLE:
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/* The pipe is already open with compatible parameters.
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Pick a new name and retry. */
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debug_printf ("pipe busy, retrying");
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*r = NULL;
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break;
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case STATUS_ACCESS_DENIED:
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/* The pipe is already open with incompatible parameters.
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Pick a new name and retry. */
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debug_printf ("pipe access denied, retrying");
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*r = NULL;
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break;
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default:
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{
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__seterrno_from_nt_status (status);
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err = GetLastError ();
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debug_printf ("failed, %E");
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*r = INVALID_HANDLE_VALUE;
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}
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}
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}
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if (err)
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{
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*r = NULL;
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return err;
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}
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if (!w)
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debug_printf ("pipe write handle NULL");
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else
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{
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debug_printf ("NtOpenFile: name %S", &pipename);
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access = GENERIC_WRITE | FILE_READ_ATTRIBUTES;
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status = NtOpenFile (w, access, &attr, &io, 0, 0);
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if (!NT_SUCCESS (status))
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{
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DWORD err = GetLastError ();
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debug_printf ("NtOpenFile failed, r %p, %E", r);
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if (r)
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CloseHandle (*r);
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*w = NULL;
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return err;
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}
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debug_printf ("pipe write handle %p", *w);
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}
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/* Success. */
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return 0;
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}
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int
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fhandler_pipe::ioctl (unsigned int cmd, void *p)
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{
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