UBUNTU-CVE-2024-50263
In the Linux kernel, the following vulnerability has been resolved: fork: only invoke khugepaged, ksm hooks if no error There is no reason to invoke these hooks early against an mm that is in an incomplete state. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. Their placement early in dup_mmap() only appears to have been meaningful for early error checking, and since functionally it'd require a very small allocation to fail (in practice 'too small to fail') that'd only occur in the most dire circumstances, meaning the fork would fail or be OOM'd in any case. Since both khugepaged and KSM tracking are there to provide optimisations to memory performance rather than critical functionality, it doesn't really matter all that much if, under such dire memory pressure, we fail to register an mm with these. As a result, we follow the example of commit d2081b2bf819 ("mm: khugepaged: make khugepaged_enter() void function") and make ksm_fork() a void function also. We only expose the mm to these functions once we are done with them and only if no error occurred in the fork operation.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
19 explicit affected versions
6 explicit affected versions
21 explicit affected versions
10 explicit affected versions
12 explicit affected versions
19 explicit affected versions
7 explicit affected versions
16 explicit affected versions
13 explicit affected versions
18 explicit affected versions
35 explicit affected versions
18 explicit affected versions
21 explicit affected versions
13 explicit affected versions
4 explicit affected versions
23 explicit affected versions
26 explicit affected versions
1 explicit affected versions
21 explicit affected versions
16 explicit affected versions
10 explicit affected versions
22 explicit affected versions
7 explicit affected versions
12 explicit affected versions
1 explicit affected versions
12 explicit affected versions
14 explicit affected versions
1 explicit affected versions
7 explicit affected versions
2 explicit affected versions
12 explicit affected versions
12 explicit affected versions
16 explicit affected versions
13 explicit affected versions
8 explicit affected versions
37 explicit affected versions
1 explicit affected versions
13 explicit affected versions
14 explicit affected versions
10 explicit affected versions
26 explicit affected versions
13 explicit affected versions
29 explicit affected versions
13 explicit affected versions
15 explicit affected versions
16 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
1 explicit affected versions
12 explicit affected versions
7 explicit affected versions
12 explicit affected versions
10 explicit affected versions
26 explicit affected versions
20 explicit affected versions
11 explicit affected versions
23 explicit affected versions
13 explicit affected versions
21 explicit affected versions
16 explicit affected versions
24 explicit affected versions
3 explicit affected versions
1 explicit affected versions
51 explicit affected versions
7 explicit affected versions
20 explicit affected versions
12 explicit affected versions
27 explicit affected versions
17 explicit affected versions
8 explicit affected versions
5 explicit affected versions
8 explicit affected versions
10 explicit affected versions
20 explicit affected versions
13 explicit affected versions
13 explicit affected versions
7 explicit affected versions
2 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
25 explicit affected versions
14 explicit affected versions
38 explicit affected versions
9 explicit affected versions
11 explicit affected versions
15 explicit affected versions
7 explicit affected versions
7 explicit affected versions
4 explicit affected versions
1 explicit affected versions
13 explicit affected versions
43 explicit affected versions
10 explicit affected versions
8 explicit affected versions
19 explicit affected versions
14 explicit affected versions
4 explicit affected versions
11 explicit affected versions
1 explicit affected versions
14 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: fork: only invoke khugepaged, ksm hooks if no error There is no reason to invoke these hooks early against an mm that is in an incomplete state. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. Their placement early in dup_mmap() only appears to have been meaningful for early error checking, and since functionally it'd require a very small allocation to fail (in practice 'too small to fail') that'd only occur in the most dire circumstances, meaning the fork would fail or be OOM'd in any case. Since both khugepaged and KSM tracking are there to provide optimisations to memory performance rather than critical functionality, it doesn't really matter all that much if, under such dire memory pressure, we fail to register an mm with these. As a result, we follow the example of commit d2081b2bf819 ("mm: khugepaged: make khugepaged_enter() void function") and make ksm_fork() a void function also. We only expose the mm to these functions once we are done with them and only if no error occurred in the fork operation.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/985da552a98e27096444508ce5d853244019111f
- https://git.kernel.org/stable/c/3b85aa0da8cd01173b9afd1f70080fbb9576c4b0
- https://git.kernel.org/stable/c/985da552a98e27096444508ce5d853244019111f
- https://ubuntu.com/security/CVE-2024-50263
- https://ubuntu.com/security/notices/USN-7276-1
- https://ubuntu.com/security/notices/USN-7277-1
- https://ubuntu.com/security/notices/USN-7310-1
- https://ubuntu.com/security/notices/USN-7449-1
- https://ubuntu.com/security/notices/USN-7449-2
- https://ubuntu.com/security/notices/USN-7450-1
- https://ubuntu.com/security/notices/USN-7451-1
- https://ubuntu.com/security/notices/USN-7452-1
- https://ubuntu.com/security/notices/USN-7453-1
- https://ubuntu.com/security/notices/USN-7468-1
- https://ubuntu.com/security/notices/USN-7523-1
- https://ubuntu.com/security/notices/USN-7524-1
- https://www.cve.org/CVERecord?id=CVE-2024-50263