[Xen-changelog] [xen stable-4.11] x86/IRQ: avoid UB (or worse) in trace_irq_mask()

[patchbot@xxxxxxx]

commit 9d89d2c431b1fd8817fb4cd20c495fe4bf6e770a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 6 14:09:56 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jun 6 14:09:56 2019 +0200

    x86/IRQ: avoid UB (or worse) in trace_irq_mask()
    
    Dynamically allocated CPU mask objects may be smaller than cpumask_t, so
    copying has to be restricted to the actual allocation size. This is
    particulary important since the function doesn't bail early when tracing
    is not active, so even production builds would be affected by potential
    misbehavior here.
    
    Take the opportunity and also
    - use initializers instead of assignment + memset(),
    - constify the cpumask_t input pointer,
    - u32 -> uint32_t.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    master commit: 6fafb8befa99620a2d7323b9eca5c387bad1f59f
    master date: 2019-05-13 16:41:03 +0200
---
 xen/arch/x86/irq.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 0ceb9b9a1c..0071b009bb 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -99,16 +99,19 @@ void unlock_vector_lock(void)
     spin_unlock(&vector_lock);
 }
 
-static void trace_irq_mask(u32 event, int irq, int vector, cpumask_t *mask)
+static void trace_irq_mask(uint32_t event, int irq, int vector,
+                           const cpumask_t *mask)
 {
     struct {
         unsigned int irq:16, vec:16;
         unsigned int mask[6];
-    } d;
-    d.irq = irq;
-    d.vec = vector;
-    memset(d.mask, 0, sizeof(d.mask));
-    memcpy(d.mask, mask, min(sizeof(d.mask), sizeof(cpumask_t)));
+    } d = {
+       .irq = irq,
+       .vec = vector,
+    };
+
+    memcpy(d.mask, mask,
+           min(sizeof(d.mask), BITS_TO_LONGS(nr_cpu_ids) * sizeof(long)));
     trace_var(event, 1, sizeof(d), &d);
 }
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.11

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