From: Kees Cook <keescook@chromium.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] docs, parallelism: Do not leak blocking mode to writer
Date: Wed, 20 Nov 2019 16:03:03 -0800 [thread overview]
Message-ID: <20191121000304.48829-3-keescook@chromium.org> (raw)
In-Reply-To: <20191121000304.48829-1-keescook@chromium.org>
Setting non-blocking via a local copy of the jobserver file descriptor
is safer than just assuming the writer on the original fd is 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>
---
scripts/jobserver-count | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/scripts/jobserver-count b/scripts/jobserver-count
index 6e15b38df3d0..a68a04ad304f 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 +25,13 @@ 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 writer.
+ reader = os.open("/proc/self/fd/%d" % (reader), os.O_RDONLY)
+ flags = fcntl.fcntl(reader, fcntl.F_GETFL)
+ fcntl.fcntl(reader, fcntl.F_SETFL, flags | 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)
--
2.17.1
next prev parent reply other threads:[~2019-11-21 0:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 0:03 [PATCH 0/3] docs, parallelism: Rearrange how jobserver reservations are made Kees Cook
2019-11-21 0:03 ` [PATCH 1/3] docs, parallelism: Fix failure path and add comment Kees Cook
2019-11-21 0:03 ` Kees Cook [this message]
2019-11-21 7:41 ` [PATCH 2/3] docs, parallelism: Do not leak blocking mode to writer Rasmus Villemoes
2019-11-21 19:09 ` Kees Cook
2019-11-21 0:03 ` [PATCH 3/3] docs, parallelism: Rearrange how jobserver reservations are made Kees Cook
2019-11-21 8:09 ` Rasmus Villemoes
2019-11-21 19:39 ` Kees Cook
2019-11-21 19:52 ` Kees Cook
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