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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id p15-20020a17090a348f00b0021952b5e9bcsm5170108pjb.53.2022.12.16.12.30.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Dec 2022 12:30:31 -0800 (PST) From: Kees Cook To: Peter Zijlstra Cc: Kees Cook , "Eric W. Biederman" , Jann Horn , Arnd Bergmann , Petr Mladek , Andrew Morton , Luis Chamberlain , Marco Elver , tangmeng , Sebastian Andrzej Siewior , Tiezhu Yang , Stafford Horne , "Guilherme G. Piccoli" , John Ogness , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] exit: Use READ_ONCE() for all oops/warn limit reads Date: Fri, 16 Dec 2022 12:30:28 -0800 Message-Id: <20221216203024.never.640-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2639; h=from:subject:message-id; bh=QFDv42gSw8RrL/kT/bLCpkDTyQ5e1mjGxtt244QW9V0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjnNVkYwcCuX3+lRp4U1y4bVoF7qP2EdUuq4JMMDD2 0AFmIzyJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCY5zVZAAKCRCJcvTf3G3AJlNcD/ 0QvyfFKYGmpjzAId3QIjrakY8NxwFTZRZWL6SjPD22tFgR90XCdBibLo6mbOWrszOVuhsYlDrc2/Tn jxZqKMuAVbU8ybDSpXio897z7ooUsCJe6RX3IKjAJ0M0ToVvnsY9o5k1VleYRZJH0FsIN+LQrda8Yh qClm/+UwCGCJV+mYCiLGqB9F/Bs2oLxUgdfOk0PBpNAewEVz46tTlLj/me8beXXtABSMY595LjRDVr zgUb5LaPaYYIGwksz33bGSsHRI+lyI05RWuG+DGLz5xHfTQtlz/zONesrX0Q8pAiqkVkoSz1qjXJEF h85OXdmGjwEQxQG+JXTySbrhnbsRg3kOTjHuiJKs93On3G2M9KFSC2vAWhENdi/zPTnGR8iyNg8UrU NmHvOIeTKSkRGu2Sr6zkhwWhAa76SqO+YGU4AtuFA7UGK2Xwuaq3YmQTvZENJyBojoRoley2Oc4n/4 Phu3zm03tPfE7mTAfowjhuKKvhEBOF54gnyP3sIrZ0dLcQ9aP1sbb2KpDaPA4pWWEQAah2OCjELhh6 ke4JhhJ/QoXAZ9w+dpjLUgniEDtnZSPvfMnDhWAn1RBfj06+om5o4RcdrjiOqcwxnyVQkDhzVk2vBq 8f2bsA4MpSbk+OhcluHRTvpxuVCD5apQLNDcCcoNYoIR5HI8bTiOUt2OXrQA== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 Link: https://lore.kernel.org/lkml/Y5x7GXeluFmZ8E0E@hirez.programming.kicks= -ass.net Fixes: 9fc9e278a5c0 ("panic: Introduce warn_limit") Fixes: d4ccd54d28d3 ("exit: Put an upper limit on how often we can oops") Cc: "Eric W. Biederman" Cc: Jann Horn Cc: Arnd Bergmann Cc: Petr Mladek Cc: Andrew Morton Cc: Luis Chamberlain Cc: Marco Elver Cc: tangmeng Cc: Sebastian Andrzej Siewior Cc: Tiezhu Yang Signed-off-by: Kees Cook Acked-by: Peter Zijlstra (Intel) --- kernel/exit.c | 6 ++++-- kernel/panic.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index deffb8e4b1b2..15dc2ec80c46 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -931,6 +931,7 @@ void __noreturn make_task_dead(int signr) * Then do everything else. */ struct task_struct *tsk =3D current; + unsigned int limit; =20 if (unlikely(in_interrupt())) panic("Aiee, killing interrupt handler!"); @@ -954,8 +955,9 @@ 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) >=3D READ_ONCE(oops_limit) && oops_lim= it) - panic("Oopsed too often (kernel.oops_limit is %d)", oops_limit); + limit =3D READ_ONCE(oops_limit); + if (atomic_inc_return(&oops_count) >=3D limit && limit) + panic("Oopsed too often (kernel.oops_limit is %d)", limit); =20 /* * We're taking recursive faults here in make_task_dead. Safest is to just diff --git a/kernel/panic.c b/kernel/panic.c index 54deb743b2d5..7834c9854e02 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -231,12 +231,15 @@ static void panic_print_sys_info(bool console_flush) =20 void check_panic_on_warn(const char *origin) { + unsigned int limit; + if (panic_on_warn) panic("%s: panic_on_warn set ...\n", origin); =20 - if (atomic_inc_return(&warn_count) >=3D READ_ONCE(warn_limit) && warn_lim= it) + limit =3D READ_ONCE(warn_limit); + if (atomic_inc_return(&warn_count) >=3D limit && limit) panic("%s: system warned too often (kernel.warn_limit is %d)", - origin, warn_limit); + origin, limit); } =20 /** --=20 2.34.1