From 5cd4b1ce2389604ef16a481ac9ff10448485f5d7 Mon Sep 17 00:00:00 2001 From: Elliot Berman Date: Wed, 11 Aug 2021 08:59:14 -0700 Subject: [PATCH] UPSTREAM: cfi: Use rcu_read_{un}lock_sched_notrace If rcu_read_lock_sched tracing is enabled, the tracing subsystem can perform a jump which needs to be checked by CFI. For example, stm_ftrace source is enabled as a module and hooks into enabled ftrace events. This can cause an recursive loop where find_shadow_check_fn -> rcu_read_lock_sched -> (call to stm_ftrace generates cfi slowpath) -> find_shadow_check_fn -> rcu_read_lock_sched -> ... To avoid the recursion, either the ftrace codes needs to be marked with __no_cfi or CFI should not trace. Use the "_notrace" in CFI to avoid tracing so that CFI can guard ftrace. Signed-off-by: Elliot Berman Reviewed-by: Sami Tolvanen Cc: stable@vger.kernel.org Fixes: cf68fffb66d6 ("add support for Clang CFI") Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20210811155914.19550-1-quic_eberman@quicinc.com Bug: 194223154 Change-Id: I7d112496c7f503f95ba69390f6454623cf6dfed2 (cherry picked from commit 14c4c8e41511aa8fba7fb239b20b6539b5bce201) Signed-off-by: Elliot Berman --- kernel/cfi.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/cfi.c b/kernel/cfi.c index ab898e0d38d0..db013eb92dd2 100644 --- a/kernel/cfi.c +++ b/kernel/cfi.c @@ -251,9 +251,9 @@ static inline cfi_check_fn __find_shadow_check_fn(unsigned long ptr) { cfi_check_fn fn; - rcu_read_lock_sched(); + rcu_read_lock_sched_notrace(); fn = ptr_to_check_fn(rcu_dereference_sched(cfi_shadow), ptr); - rcu_read_unlock_sched(); + rcu_read_unlock_sched_notrace(); return fn; } @@ -272,11 +272,11 @@ static inline cfi_check_fn __find_module_check_fn(unsigned long ptr) cfi_check_fn fn = NULL; struct module *mod; - rcu_read_lock_sched(); + rcu_read_lock_sched_notrace(); mod = __module_address(ptr); if (mod) fn = mod->cfi_check; - rcu_read_unlock_sched(); + rcu_read_unlock_sched_notrace(); return fn; }