d9937b62e0
chrony calls getrandom() at startup if available, so it needs a workaround
for the blocking behaviour on recent (4.14.39+), similar to what was done
for util-linux in commit c4d86707cd (util-linux: add two upstream patches
to fix blocking on getrandom() with recent kernels).
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
43 lines
1.5 KiB
Diff
43 lines
1.5 KiB
Diff
From 7c5bd948bb7e21fa0ee22f29e97748b2d0360319 Mon Sep 17 00:00:00 2001
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From: Miroslav Lichvar <mlichvar@redhat.com>
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Date: Thu, 17 May 2018 14:16:58 +0200
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Subject: [PATCH] util: fall back to reading /dev/urandom when getrandom()
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blocks
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With recent changes in the Linux kernel, the getrandom() system call may
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block for a long time after boot on machines that don't have enough
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entropy. It blocks the chronyd's initialization before it can detach
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from the terminal and may cause a chronyd service to fail to start due
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to a timeout.
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At least for now, enable the GRND_NONBLOCK flag to make the system call
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non-blocking and let the code fall back to reading /dev/urandom (which
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never blocks) if the system call failed with EAGAIN or any other error.
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This makes the start of chronyd non-deterministic with respect to files
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that it needs to open and possibly also makes it slightly easier to
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guess the transmit/receive timestamp in client requests until the
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urandom source is fully initialized.
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Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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---
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util.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/util.c b/util.c
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index 4b3e455..76417d5 100644
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--- a/util.c
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+++ b/util.c
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@@ -1224,7 +1224,7 @@ get_random_bytes_getrandom(char *buf, unsigned int len)
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if (disabled)
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break;
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- if (getrandom(rand_buf, sizeof (rand_buf), 0) != sizeof (rand_buf)) {
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+ if (getrandom(rand_buf, sizeof (rand_buf), GRND_NONBLOCK) != sizeof (rand_buf)) {
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disabled = 1;
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break;
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}
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--
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2.11.0
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