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Re: [PATCH] migration/dirtyrate: Fix segmentation fault


From: Yong Huang
Subject: Re: [PATCH] migration/dirtyrate: Fix segmentation fault
Date: Tue, 23 Apr 2024 15:12:47 +0800



On Tue, Apr 23, 2024 at 2:19 PM Masato Imai <mii@sfc.wide.ad.jp> wrote:
When the KVM acceleration parameter is not set, executing calc_dirty_rate
with the -r option results in a segmentation fault due to accessing a
null kvm_state pointer in the kvm_dirty_rate_enabled function.
 
s/kvm_dirty_rate_enabled/kvm_dirty_ring_enabled/

This commit adds a check for kvm_enabled to prevent segmentation faults.

Signed-off-by: Masato Imai <mii@sfc.wide.ad.jp>
---
 migration/dirtyrate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 1d2e85746f..4c1579c6e9 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -800,6 +800,8 @@ void qmp_calc_dirty_rate(int64_t calc_time,
      * on the contrary, dirty bitmap mode is not.
      */ 
 
     if (((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
+        !kvm_enabled()) ||
+        ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
         !kvm_dirty_ring_enabled()) ||
         ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) && 
          kvm_dirty_ring_enabled())) {

This path may result in segmentation fault likewise, we can fix it together
by adding the following logic before this code:

    if (!kvm_enabled() &&
       (mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING ||
        mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP)) {
        error_setg(errp, ...
        return;
    }

 
--
2.34.1


Thanks for your work,
Yong

--
Best regards

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