From: bugzilla-daemon@bugzilla.kernel.org
To: linux-man@vger.kernel.org
Subject: [Bug 214885] New: random.{4,7} [man-pages 5.13] do not reflect changes to /dev/random semantics since kernel 5.6
Date: Sat, 30 Oct 2021 16:42:02 +0000 [thread overview]
Message-ID: <bug-214885-11311@https.bugzilla.kernel.org/> (raw)
https://bugzilla.kernel.org/show_bug.cgi?id=214885
Bug ID: 214885
Summary: random.{4,7} [man-pages 5.13] do not reflect changes
to /dev/random semantics since kernel 5.6
Product: Documentation
Version: unspecified
Hardware: All
OS: Linux
Status: NEW
Severity: low
Priority: P1
Component: man-pages
Assignee: documentation_man-pages@kernel-bugs.osdl.org
Reporter: kerbug@zplane.com
Regression: No
In kernel 5.6, the semantics of reading from /dev/random were changed
significantly [1][2]. If my understanding of [1] is correct -- and perhaps it
is not, I am not claiming any expertise -- /dev/random now behaves essentially
like /dev/urandom, except that it blocks only in the case of insufficient
initial entropy during boot, but never blocks thereafter. A few quick
experiments using kernel 5.14.14 seem to confirm that understanding.
This is a significant behavioral change but it does not seem to be reflected in
either random.4 or random.7 from man-pages release 5.13 (as provided in Arch
Linux man-pages 5.13-1). In looking thru the change history of those pages, it
does not seem that there have been any updates to either since man-pages 4.10.
I'd be happy to offer a patch, but the required changes are not trivial and am
hestitant to contribute language on something that I don't have sufficient
familiarity with.
Based on my quick experiments with kernel 5.14.14, at least the following
statements in random.4 seem to be entirely invalidated by the post 5.6
behavior:
A read(2) from /dev/random will return at most 512 bytes (340
bytes on Linux kernels before version 2.6.12):
Observed behavior with 5.14.14: It returns up to 32MB, just as
/dev/urandom does.
The subsection describing read_wakeup_threshold:
This pseudo-file read_wakeup_threshold no longer exists in
/proc/sys/kernel/random.
- Glenn
[1]
https://github.com/torvalds/linux/commit/30c08efec8884fb106b8e57094baa51bb4c44e32
[2] https://lwn.net/Articles/808575/
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next reply other threads:[~2021-10-30 16:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-30 16:42 bugzilla-daemon [this message]
2021-10-30 17:01 ` [Bug 214885] random.{4,7} [man-pages 5.13] do not reflect changes to /dev/random semantics since kernel 5.6 bugzilla-daemon
2023-05-25 11:34 ` bugzilla-daemon
2023-05-25 12:36 ` bugzilla-daemon
2023-05-29 8:50 ` [PATCH] random.{4,7}, getrandom.2: Adapt to Linux 5.6 changes Mingye Wang
2023-05-31 22:20 ` Alejandro Colomar
2023-06-02 11:35 ` Mingye Wang
2023-06-05 3:13 ` Mingye Wang
2023-07-08 19:06 ` Alejandro Colomar
2024-03-25 12:44 ` [Bug 214885] random.{4,7} [man-pages 5.13] do not reflect changes to /dev/random semantics since kernel 5.6 bugzilla-daemon
2024-03-25 13:26 ` bugzilla-daemon
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