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      <title>CVE-2024-57877 — arm64: ptrace: fix partial SETREGSET for NT_ARM_POE</title>
      <link>https://vulnerability.circl.lu/vuln/cve-2024-57877</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;arm64: ptrace: fix partial SETREGSET for NT_ARM_POE&lt;/p&gt;
&lt;p&gt;Currently poe_set() doesn&amp;#39;t initialize the temporary &amp;#39;ctrl&amp;#39; variable,
and a SETREGSET call with a length of zero will leave this
uninitialized. Consequently an arbitrary value will be written back to
target-&amp;gt;thread.por_el0, potentially leaking up to 64 bits of memory from
the kernel stack. The read is limited to a specific slot on the stack,
and the issue does not provide a write mechanism.&lt;/p&gt;
&lt;p&gt;Fix this by initializing the temporary value before copying the regset
from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG,
NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing
contents of POR_EL1 will be retained.&lt;/p&gt;
&lt;p&gt;Before this patch:&lt;/p&gt;
&lt;p&gt;| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d
|
| Attempting to write NT_ARM_POE (zero length)
| SETREGSET(nt=0x40f, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0xffff8000839c3d50&lt;/p&gt;
&lt;p&gt;After this patch:&lt;/p&gt;
&lt;p&gt;| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT…&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;arm64: ptrace: fix partial SETREGSET for NT_ARM_POE&lt;/p&gt;
&lt;p&gt;Currently poe_set() doesn&amp;#39;t initialize the temporary &amp;#39;ctrl&amp;#39; variable,
and a SETREGSET call with a length of zero will leave this
uninitialized. Consequently an arbitrary value will be written back to
target-&amp;gt;thread.por_el0, potentially leaking up to 64 bits of memory from
the kernel stack. The read is limited to a specific slot on the stack,
and the issue does not provide a write mechanism.&lt;/p&gt;
&lt;p&gt;Fix this by initializing the temporary value before copying the regset
from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG,
NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing
contents of POR_EL1 will be retained.&lt;/p&gt;
&lt;p&gt;Before this patch:&lt;/p&gt;
&lt;p&gt;| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d
|
| Attempting to write NT_ARM_POE (zero length)
| SETREGSET(nt=0x40f, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0xffff8000839c3d50&lt;/p&gt;
&lt;p&gt;After this patch:&lt;/p&gt;
&lt;p&gt;| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT…&lt;/p&gt;</content:encoded>
      <guid isPermaLink="false">https://vulnerability.circl.lu/vuln/cve-2024-57877</guid>
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