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    <lastBuildDate>Wed, 07 Oct 2026 22:29:43 +0000</lastBuildDate>
    <item>
      <title>CVE-2022-49052 — mm: fix unexpected zeroed page mapping with zram swap</title>
      <link>https://cve.radiocsirt.org/vuln/cve-2022-49052</link>
      <description>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;mm: fix unexpected zeroed page mapping with zram swap&lt;/p&gt;
&lt;p&gt;Two processes under CLONE_VM cloning, user process can be corrupted by
seeing zeroed page unexpectedly.&lt;/p&gt;
&lt;p&gt;CPU A                        CPU B&lt;/p&gt;
&lt;p&gt;do_swap_page                do_swap_page
  SWP_SYNCHRONOUS_IO path     SWP_SYNCHRONOUS_IO path
  swap_readpage valid data
    swap_slot_free_notify
      delete zram entry
                              swap_readpage zeroed(invalid) data
                              pte_lock
                              map the *zero data* to userspace
                              pte_unlock
  pte_lock
  if (!pte_same)
    goto out_nomap;
  pte_unlock
  return and next refault will
  read zeroed data&lt;/p&gt;
&lt;p&gt;The swap_slot_free_notify is bogus for CLONE_VM case since it doesn&amp;#39;t
increase the refcount of swap slot at copy_mm so it couldn&amp;#39;t catch up
whether it&amp;#39;s safe or not to discard data from backing device.  In the
case, only the lock it could rely on to synchronize swap slot freeing is
page table lock.  Thus, this patch gets rid of the swap_slot_free_notify
function.  With this patch, CPU A will see correct data.&lt;/p&gt;
&lt;p&gt;CPU A                        CPU B&lt;/p&gt;
&lt;p&gt;do_swap_page                do_swap_page
  SWP_SYNCHRONOUS_IO path     SWP_SYNCHRONOUS_IO path
                              swap_readpage original data
                              pte_lock
                              map the original data
                              sw…&lt;/p&gt;</description>
      <content:encoded>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;mm: fix unexpected zeroed page mapping with zram swap&lt;/p&gt;
&lt;p&gt;Two processes under CLONE_VM cloning, user process can be corrupted by
seeing zeroed page unexpectedly.&lt;/p&gt;
&lt;p&gt;CPU A                        CPU B&lt;/p&gt;
&lt;p&gt;do_swap_page                do_swap_page
  SWP_SYNCHRONOUS_IO path     SWP_SYNCHRONOUS_IO path
  swap_readpage valid data
    swap_slot_free_notify
      delete zram entry
                              swap_readpage zeroed(invalid) data
                              pte_lock
                              map the *zero data* to userspace
                              pte_unlock
  pte_lock
  if (!pte_same)
    goto out_nomap;
  pte_unlock
  return and next refault will
  read zeroed data&lt;/p&gt;
&lt;p&gt;The swap_slot_free_notify is bogus for CLONE_VM case since it doesn&amp;#39;t
increase the refcount of swap slot at copy_mm so it couldn&amp;#39;t catch up
whether it&amp;#39;s safe or not to discard data from backing device.  In the
case, only the lock it could rely on to synchronize swap slot freeing is
page table lock.  Thus, this patch gets rid of the swap_slot_free_notify
function.  With this patch, CPU A will see correct data.&lt;/p&gt;
&lt;p&gt;CPU A                        CPU B&lt;/p&gt;
&lt;p&gt;do_swap_page                do_swap_page
  SWP_SYNCHRONOUS_IO path     SWP_SYNCHRONOUS_IO path
                              swap_readpage original data
                              pte_lock
                              map the original data
                              sw…&lt;/p&gt;</content:encoded>
      <guid isPermaLink="false">https://cve.radiocsirt.org/vuln/cve-2022-49052</guid>
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