This is a note to let you know that I've just added the patch titled

x86/uaccess, sched/preempt: Verify access_ok() context

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-uaccess-sched-preempt-verify-access_ok-context.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 7c4788950ba5922fde976d80b72baf46f14dee8d Mon Sep 17 00:00:00 2001

From: Peter Zijlstra peterz@infradead.org Date: Tue, 22 Nov 2016 10:57:15 +0100 Subject: x86/uaccess, sched/preempt: Verify access_ok() context

From: Peter Zijlstra peterz@infradead.org

commit 7c4788950ba5922fde976d80b72baf46f14dee8d upstream.

I recently encountered wreckage because access_ok() was used where it should not be, add an explicit WARN when access_ok() is used wrongly.

Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Andy Lutomirski luto@amacapital.net Cc: H. Peter Anvin hpa@zytor.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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 @@ -66,6 +66,12 @@ static inline bool __chk_range_not_ok(un __chk_range_not_ok((unsigned long __force)(addr), size, limit); \ })

+#ifdef CONFIG_DEBUG_ATOMIC_SLEEP +# define WARN_ON_IN_IRQ() WARN_ON_ONCE(!in_task()) +#else +# define WARN_ON_IN_IRQ() +#endif + /** * access_ok: - Checks if a user space pointer is valid * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that @@ -86,8 +92,11 @@ 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) \ +({ \ + WARN_ON_IN_IRQ(); \ + likely(!__range_not_ok(addr, size, user_addr_max())); \ +})

/* * The exception table consists of pairs of addresses relative to the --- 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();

Patches currently in stable-queue which might be from peterz@infradead.org are

queue-4.4/x86-uaccess-sched-preempt-verify-access_ok-context.patch