On Tue, Nov 22, 2016 at 11:42:19AM -0800, Linus Torvalds wrote: > On Tue, Nov 22, 2016 at 11:37 AM, Peter Zijlstra <[email protected]> wrote: > > > > CONFIG_DEBUG_VM seems somehow inappropriate. > > The usual might_fault() logic? That uses > > defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP) > > (and "might_sleep()" uses just CONFIG_DEBUG_ATOMIC_SLEEP, maybe that's fine). >
Fair enough; something like so then? --- Subject: x86: Verify access_ok() context From: Peter Zijlstra <[email protected]> Date: Tue, 22 Nov 2016 10:57:15 +0100 I recently encountered wreckage because access_ok() was used where it should not be, add an explicit WARN when access_ok() is used wrongly. Cc: Andy Lutomirski <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> --- arch/x86/include/asm/uaccess.h | 13 +++++++++++-- include/linux/preempt.h | 21 +++++++++++++-------- 2 files changed, 24 insertions(+), 10 deletions(-) --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -68,6 +68,12 @@ static inline bool __chk_range_not_ok(un __chk_range_not_ok((unsigned long __force)(addr), size, limit); \ }) +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP +#define ACCESS_OK_WARN() WARN_ON_ONCE(!in_task()) +#else +#define ACCESS_OK_WARN() +#endif + /** * access_ok: - Checks if a user space pointer is valid * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that @@ -88,8 +94,11 @@ static inline bool __chk_range_not_ok(un * checks that the pointer is in the user space range - after calling * this function, memory access functions may still return -EFAULT. */ -#define access_ok(type, addr, size) \ - likely(!__range_not_ok(addr, size, user_addr_max())) +#define access_ok(type, addr, size) \ +({ \ + ACCESS_OK_WARN(); \ + likely(!__range_not_ok(addr, size, user_addr_max())); \ +}) /* * These are the main single-value transfer routines. They automatically --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -65,19 +65,24 @@ /* * Are we doing bottom half or hardware interrupt processing? - * Are we in a softirq context? Interrupt context? - * in_softirq - Are we currently processing softirq or have bh disabled? - * in_serving_softirq - Are we currently processing softirq? + * + * in_irq() - We're in (hard) IRQ context + * in_softirq() - We have BH disabled, or are processing softirqs + * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled + * in_serving_softirq() - We're in softirq context + * in_nmi() - We're in NMI context + * in_task() - We're in task context + * + * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really + * should not be used in new code. */ #define in_irq() (hardirq_count()) #define in_softirq() (softirq_count()) #define in_interrupt() (irq_count()) #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) - -/* - * Are we in NMI context? - */ -#define in_nmi() (preempt_count() & NMI_MASK) +#define in_nmi() (preempt_count() & NMI_MASK) +#define in_task() (!(preempt_count() & \ + (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) /* * The preempt_count offset after preempt_disable();
