This is a note to let you know that I've just added the patch titled
exit: Use READ_ONCE() for all oops/warn limit reads
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
exit-use-read_once-for-all-oops-warn-limit-reads.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable-owner@xxxxxxxxxxxxxxx Fri Feb 3 01:28:56 2023
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Thu, 2 Feb 2023 16:27:17 -0800
Subject: exit: Use READ_ONCE() for all oops/warn limit reads
To: stable@xxxxxxxxxxxxxxx
Cc: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, SeongJae Park <sj@xxxxxxxxxx>, Seth Jenkins <sethjenkins@xxxxxxxxxx>, Jann Horn <jannh@xxxxxxxxxx>, "Eric W . Biederman" <ebiederm@xxxxxxxxxxxx>, linux-hardening@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, Petr Mladek <pmladek@xxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Luis Chamberlain <mcgrof@xxxxxxxxxx>, Marco Elver <elver@xxxxxxxxxx>, tangmeng <tangmeng@xxxxxxxxxxxxx>, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>, Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Message-ID: <20230203002717.49198-16-ebiggers@xxxxxxxxxx>
From: Kees Cook <keescook@xxxxxxxxxxxx>
commit 7535b832c6399b5ebfc5b53af5c51dd915ee2538 upstream.
Use a temporary variable to take full advantage of READ_ONCE() behavior.
Without this, the report (and even the test) might be out of sync with
the initial test.
Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/Y5x7GXeluFmZ8E0E@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 9fc9e278a5c0 ("panic: Introduce warn_limit")
Fixes: d4ccd54d28d3 ("exit: Put an upper limit on how often we can oops")
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: tangmeng <tangmeng@xxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 6 ++++--
kernel/panic.c | 7 +++++--
2 files changed, 9 insertions(+), 4 deletions(-)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -975,6 +975,7 @@ void __noreturn make_task_dead(int signr
* Take the task off the cpu after something catastrophic has
* happened.
*/
+ unsigned int limit;
/*
* Every time the system oopses, if the oops happens while a reference
@@ -986,8 +987,9 @@ void __noreturn make_task_dead(int signr
* To make sure this can't happen, place an upper bound on how often the
* kernel may oops without panic().
*/
- if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit)
- panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit);
+ limit = READ_ONCE(oops_limit);
+ if (atomic_inc_return(&oops_count) >= limit && limit)
+ panic("Oopsed too often (kernel.oops_limit is %d)", limit);
do_exit(signr);
}
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -168,12 +168,15 @@ EXPORT_SYMBOL(nmi_panic);
void check_panic_on_warn(const char *origin)
{
+ unsigned int limit;
+
if (panic_on_warn)
panic("%s: panic_on_warn set ...\n", origin);
- if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit) && warn_limit)
+ limit = READ_ONCE(warn_limit);
+ if (atomic_inc_return(&warn_count) >= limit && limit)
panic("%s: system warned too often (kernel.warn_limit is %d)",
- origin, warn_limit);
+ origin, limit);
}
/**
Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are
queue-4.19/panic-unset-panic_on_warn-inside-panic.patch
queue-4.19/objtool-add-a-missing-comma-to-avoid-string-concatenation.patch
queue-4.19/hexagon-fix-function-name-in-die.patch
queue-4.19/exit-add-and-use-make_task_dead.patch
queue-4.19/h8300-fix-build-errors-from-do_exit-to-make_task_dead-transition.patch
queue-4.19/panic-consolidate-open-coded-panic_on_warn-checks.patch
queue-4.19/exit-put-an-upper-limit-on-how-often-we-can-oops.patch
queue-4.19/panic-introduce-warn_limit.patch
queue-4.19/exit-allow-oops_limit-to-be-disabled.patch
queue-4.19/ia64-make-ia64_mca_recovery-bool-instead-of-tristate.patch
queue-4.19/exit-use-read_once-for-all-oops-warn-limit-reads.patch
queue-4.19/exit-expose-oops_count-to-sysfs.patch
queue-4.19/panic-expose-warn_count-to-sysfs.patch
queue-4.19/docs-fix-path-paste-o-for-sys-kernel-warn_count.patch
queue-4.19/sysctl-add-a-new-register_sysctl_init-interface.patch
