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cfi: Fix __cfi_slowpath_diag RCU usage with cpuidle

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RCU_NONIDLE usage during __cfi_slowpath_diag can result in an invalid
RCU state in the cpuidle code path:

  WARNING: CPU: 1 PID: 0 at kernel/rcu/tree.c:613 rcu_eqs_enter+0xe4/0x138
  ...
  Call trace:
    rcu_eqs_enter+0xe4/0x138
    rcu_idle_enter+0xa8/0x100
    cpuidle_enter_state+0x154/0x3a8
    cpuidle_enter+0x3c/0x58
    do_idle.llvm.6590768638138871020+0x1f4/0x2ec
    cpu_startup_entry+0x28/0x2c
    secondary_start_kernel+0x1b8/0x220
    __secondary_switched+0x94/0x98

Instead, call rcu_irq_enter/exit to wake up RCU only when needed and
disable interrupts for the entire CFI shadow/module check when we do.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20220531175910.890307-1-samitolvanen@google.com
Fixes: cf68fffb66 ("add support for Clang CFI")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Sami Tolvanen 2022-05-31 10:59:10 -07:00 committed by Kees Cook
parent b13baccc38
commit 57cd6d157e
1 changed files with 16 additions and 6 deletions
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22
kernel/cfi.c
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@ -281,6 +281,8 @@ static inline cfi_check_fn find_module_check_fn(unsigned long ptr)
static inline cfi_check_fn find_check_fn(unsigned long ptr)
{
cfi_check_fn fn = NULL;
unsigned long flags;
bool rcu_idle;
if (is_kernel_text(ptr))
return __cfi_check;
@ -290,13 +292,21 @@ static inline cfi_check_fn find_check_fn(unsigned long ptr)
* the shadow and __module_address use RCU, so we need to wake it
* up if necessary.
*/
RCU_NONIDLE({
if (IS_ENABLED(CONFIG_CFI_CLANG_SHADOW))
fn = find_shadow_check_fn(ptr);
rcu_idle = !rcu_is_watching();
if (rcu_idle) {
local_irq_save(flags);
rcu_irq_enter();
}
if (!fn)
fn = find_module_check_fn(ptr);
});
if (IS_ENABLED(CONFIG_CFI_CLANG_SHADOW))
fn = find_shadow_check_fn(ptr);
if (!fn)
fn = find_module_check_fn(ptr);
if (rcu_idle) {
rcu_irq_exit();
local_irq_restore(flags);
}
return fn;
}