Documentation/admin-guide/sysctl/kernel.rst | 5 +++-- kernel/exit.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-)
In preparation for keeping oops_limit logic in sync with warn_limit,
have oops_limit == 0 disable checking the Oops counter.
Cc: Jann Horn <jannh@google.com>
Cc: Seth Jenkins <sethjenkins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
I've changed the warn_limit logic to match...
---
Documentation/admin-guide/sysctl/kernel.rst | 5 +++--
kernel/exit.c | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 09f3fb2f8585..a31d8d81ea07 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -671,8 +671,9 @@ oops_limit
==========
Number of kernel oopses after which the kernel should panic when
-``panic_on_oops`` is not set. Setting this to 0 or 1 has the same effect
-as setting ``panic_on_oops=1``.
+``panic_on_oops`` is not set. Setting this to 0 disables checking
+the count. Setting this to 1 has the same effect as setting
+``panic_on_oops=1``. The default value is 10000.
osrelease, ostype & version
diff --git a/kernel/exit.c b/kernel/exit.c
index dc1a32149f94..deffb8e4b1b2 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -954,7 +954,7 @@ 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))
+ if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit)
panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit);
/*
--
2.34.1
On Fri, Dec 02, 2022 at 01:06:21PM -0800, Kees Cook wrote: > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -954,7 +954,7 @@ 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)) > + if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit) > panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); > That's dodgy, please write as: limit = READ_ONCE(oops_limit); if (atomic_inc_return(&oops_count) >= limit && limit) So we don't explicitly add a reload that negates the whole READ_ONCE().
On Fri, Dec 16, 2022 at 03:05:13PM +0100, Peter Zijlstra wrote: > On Fri, Dec 02, 2022 at 01:06:21PM -0800, Kees Cook wrote: > > > --- a/kernel/exit.c > > +++ b/kernel/exit.c > > @@ -954,7 +954,7 @@ 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)) > > + if (atomic_inc_return(&oops_count) >= READ_ONCE(oops_limit) && oops_limit) > > panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); > > > > That's dodgy, please write as: > > limit = READ_ONCE(oops_limit); > if (atomic_inc_return(&oops_count) >= limit && limit) > > So we don't explicitly add a reload that negates the whole READ_ONCE(). Yup, that's more correct. Sent: https://lore.kernel.org/lkml/20221216203024.never.640-kees@kernel.org -- Kees Cook
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