diff options
| author | Kees Cook <keescook@chromium.org> | 2019-11-21 12:59:28 -0800 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2019-11-22 10:35:14 -0700 |
| commit | dffd011480d727a819c537edf3b90ef063731725 (patch) | |
| tree | 965ea41e24cbbeb978dc436d8cb28f70871d8f33 /scripts | |
| parent | 4920323cffc0fe10ac107ab3e94d1bd218a678d9 (diff) | |
docs, parallelism: Do not leak blocking mode to other readers
Setting non-blocking via a local copy of the jobserver file descriptor
is safer than just assuming other reader processes with the same fd open
are prepared for it to be non-blocking.
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/lkml/44c01043-ab24-b4de-6544-e8efd153e27a@rasmusvillemoes.dk
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20191121205929.40371-3-keescook@chromium.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'scripts')
| -rwxr-xr-x | scripts/jobserver-count | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/scripts/jobserver-count b/scripts/jobserver-count index 6e15b38df3d0..7807bfa7dafa 100755 --- a/scripts/jobserver-count +++ b/scripts/jobserver-count @@ -12,12 +12,6 @@ default="1" if len(sys.argv) > 1: default=sys.argv[1] -# Set non-blocking for a given file descriptor. -def nonblock(fd): - flags = fcntl.fcntl(fd, fcntl.F_GETFL) - fcntl.fcntl(fd, fcntl.F_SETFL, flags | os.O_NONBLOCK) - return fd - # Extract and prepare jobserver file descriptors from envirnoment. try: # Fetch the make environment options. @@ -31,8 +25,12 @@ try: # Parse out R,W file descriptor numbers and set them nonblocking. fds = opts[0].split("=", 1)[1] reader, writer = [int(x) for x in fds.split(",", 1)] - reader = nonblock(reader) -except (KeyError, IndexError, ValueError, IOError): + # Open a private copy of reader to avoid setting nonblocking + # on an unexpecting process with the same reader fd. + reader = os.open("/proc/self/fd/%d" % (reader), + os.O_RDONLY | os.O_NONBLOCK) +except (KeyError, IndexError, ValueError, IOError, OSError) as e: + print(e, file=sys.stderr) # Any missing environment strings or bad fds should result in just # using the default specified parallelism. print(default) |