UBUNTU-CVE-2024-36943
In the Linux kernel, the following vulnerability has been resolved: fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan make_uffd_wp_pte() was previously doing: pte = ptep_get(ptep); ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte); But if another thread accessed or dirtied the pte between the first 2 calls, this could lead to loss of that information. Since ptep_modify_prot_start() gets and clears atomically, the following is the correct pattern and prevents any possible race. Any access after the first call would see an invalid pte and cause a fault: pte = ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte);
02 / AFFECTED SOFTWARE
Affected packages
50 explicit affected versions
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1 explicit affected versions
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13 explicit affected versions
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23 explicit affected versions
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9 explicit affected versions
16 explicit affected versions
10 explicit affected versions
3 explicit affected versions
51 explicit affected versions
7 explicit affected versions
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10 explicit affected versions
6 explicit affected versions
13 explicit affected versions
7 explicit affected versions
10 explicit affected versions
12 explicit affected versions
44 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
37 explicit affected versions
10 explicit affected versions
38 explicit affected versions
9 explicit affected versions
11 explicit affected versions
2 explicit affected versions
7 explicit affected versions
4 explicit affected versions
43 explicit affected versions
10 explicit affected versions
8 explicit affected versions
5 explicit affected versions
14 explicit affected versions
4 explicit affected versions
1 explicit affected versions
3 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: fs/proc/task_mmu: fix loss of young/dirty bits during pagemap scan make_uffd_wp_pte() was previously doing: pte = ptep_get(ptep); ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte); But if another thread accessed or dirtied the pte between the first 2 calls, this could lead to loss of that information. Since ptep_modify_prot_start() gets and clears atomically, the following is the correct pattern and prevents any possible race. Any access after the first call would see an invalid pte and cause a fault: pte = ptep_modify_prot_start(ptep); pte = pte_mkuffd_wp(pte); ptep_modify_prot_commit(ptep, pte);
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/c70dce4982ce1718bf978a35f8e26160b82081f4
- https://git.kernel.org/stable/c/74b3d66f91d9f539f99faad74d796fa9a389a015
- https://git.kernel.org/stable/c/c70dce4982ce1718bf978a35f8e26160b82081f4
- https://ubuntu.com/security/CVE-2024-36943
- https://ubuntu.com/security/notices/USN-6949-1
- https://ubuntu.com/security/notices/USN-6949-2
- https://ubuntu.com/security/notices/USN-6952-1
- https://ubuntu.com/security/notices/USN-6952-2
- https://ubuntu.com/security/notices/USN-6955-1
- https://www.cve.org/CVERecord?id=CVE-2024-36943