UBUNTU-CVE-2024-43892
In the Linux kernel, the following vulnerability has been resolved: memcg: protect concurrent access to mem_cgroup_idr Commit 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure after many small jobs") decoupled the memcg IDs from the CSS ID space to fix the cgroup creation failures. It introduced IDR to maintain the memcg ID space. The IDR depends on external synchronization mechanisms for modifications. For the mem_cgroup_idr, the idr_alloc() and idr_replace() happen within css callback and thus are protected through cgroup_mutex from concurrent modifications. However idr_remove() for mem_cgroup_idr was not protected against concurrency and can be run concurrently for different memcgs when they hit their refcnt to zero. Fix that. We have been seeing list_lru based kernel crashes at a low frequency in our fleet for a long time. These crashes were in different part of list_lru code including list_lru_add(), list_lru_del() and reparenting code. Upon further inspection, it looked like for a given object (dentry and inode), the super_block's list_lru didn't have list_lru_one for the memcg of that object. The initial suspicions were either the object is not allocated through kmem_cache_alloc_lru() or somehow memcg_list_lru_alloc() failed to allocate list_lru_one() for a memcg but returned success. No evidence were found for these cases. Looking more deeply, we started seeing situations where valid memcg's id is not present in mem_cgroup_idr and in some cases multiple valid memcgs have same id and mem_cgroup_idr is pointing to one of them. So, the most reasonable explanation is that these situations can happen due to race between multiple idr_remove() calls or race between idr_alloc()/idr_replace() and idr_remove(). These races are causing multiple memcgs to acquire the same ID and then offlining of one of them would cleanup list_lrus on the system for all of them. Later access from other memcgs to the list_lru cause crashes due to missing list_lru_one.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
33 explicit affected versions
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8 explicit affected versions
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7 explicit affected versions
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9 explicit affected versions
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13 explicit affected versions
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35 explicit affected versions
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100 explicit affected versions
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99 explicit affected versions
13 explicit affected versions
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1 explicit affected versions
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54 explicit affected versions
16 explicit affected versions
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12 explicit affected versions
45 explicit affected versions
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12 explicit affected versions
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12 explicit affected versions
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172 explicit affected versions
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37 explicit affected versions
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90 explicit affected versions
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102 explicit affected versions
18 explicit affected versions
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33 explicit affected versions
23 explicit affected versions
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1 explicit affected versions
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58 explicit affected versions
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3 explicit affected versions
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67 explicit affected versions
12 explicit affected versions
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30 explicit affected versions
1 explicit affected versions
19 explicit affected versions
5 explicit affected versions
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1 explicit affected versions
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13 explicit affected versions
13 explicit affected versions
89 explicit affected versions
13 explicit affected versions
53 explicit affected versions
76 explicit affected versions
50 explicit affected versions
10 explicit affected versions
14 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
44 explicit affected versions
37 explicit affected versions
17 explicit affected versions
14 explicit affected versions
8 explicit affected versions
38 explicit affected versions
47 explicit affected versions
9 explicit affected versions
47 explicit affected versions
11 explicit affected versions
55 explicit affected versions
7 explicit affected versions
28 explicit affected versions
82 explicit affected versions
61 explicit affected versions
125 explicit affected versions
104 explicit affected versions
4 explicit affected versions
1 explicit affected versions
1 explicit affected versions
53 explicit affected versions
97 explicit affected versions
13 explicit affected versions
43 explicit affected versions
55 explicit affected versions
128 explicit affected versions
149 explicit affected versions
10 explicit affected versions
8 explicit affected versions
12 explicit affected versions
14 explicit affected versions
90 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
51 explicit affected versions
10 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: memcg: protect concurrent access to mem_cgroup_idr Commit 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure after many small jobs") decoupled the memcg IDs from the CSS ID space to fix the cgroup creation failures. It introduced IDR to maintain the memcg ID space. The IDR depends on external synchronization mechanisms for modifications. For the mem_cgroup_idr, the idr_alloc() and idr_replace() happen within css callback and thus are protected through cgroup_mutex from concurrent modifications. However idr_remove() for mem_cgroup_idr was not protected against concurrency and can be run concurrently for different memcgs when they hit their refcnt to zero. Fix that. We have been seeing list_lru based kernel crashes at a low frequency in our fleet for a long time. These crashes were in different part of list_lru code including list_lru_add(), list_lru_del() and reparenting code. Upon further inspection, it looked like for a given object (dentry and inode), the super_block's list_lru didn't have list_lru_one for the memcg of that object. The initial suspicions were either the object is not allocated through kmem_cache_alloc_lru() or somehow memcg_list_lru_alloc() failed to allocate list_lru_one() for a memcg but returned success. No evidence were found for these cases. Looking more deeply, we started seeing situations where valid memcg's id is not present in mem_cgroup_idr and in some cases multiple valid memcgs have same id and mem_cgroup_idr is pointing to one of them. So, the most reasonable explanation is that these situations can happen due to race between multiple idr_remove() calls or race between idr_alloc()/idr_replace() and idr_remove(). These races are causing multiple memcgs to acquire the same ID and then offlining of one of them would cleanup list_lrus on the system for all of them. Later access from other memcgs to the list_lru cause crashes due to missing list_lru_one.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/9972605a238339b85bd16b084eed5f18414d22db
- https://git.kernel.org/stable/c/37a060b64ae83b76600d187d76591ce488ab836b
- https://git.kernel.org/stable/c/51c0b1bb7541f8893ec1accba59eb04361a70946
- https://git.kernel.org/stable/c/9972605a238339b85bd16b084eed5f18414d22db
- https://ubuntu.com/security/CVE-2024-43892
- https://ubuntu.com/security/notices/USN-7100-1
- https://ubuntu.com/security/notices/USN-7100-2
- https://ubuntu.com/security/notices/USN-7123-1
- https://ubuntu.com/security/notices/USN-7144-1
- https://ubuntu.com/security/notices/USN-7154-1
- https://ubuntu.com/security/notices/USN-7154-2
- https://ubuntu.com/security/notices/USN-7155-1
- https://ubuntu.com/security/notices/USN-7156-1
- https://ubuntu.com/security/notices/USN-7173-1
- https://ubuntu.com/security/notices/USN-7173-2
- https://ubuntu.com/security/notices/USN-7173-3
- https://ubuntu.com/security/notices/USN-7194-1
- https://ubuntu.com/security/notices/USN-7195-1
- https://ubuntu.com/security/notices/USN-7195-2
- https://ubuntu.com/security/notices/USN-7196-1
- https://ubuntu.com/security/notices/USN-7332-1
- https://ubuntu.com/security/notices/USN-7332-2
- https://ubuntu.com/security/notices/USN-7332-3
- https://ubuntu.com/security/notices/USN-7342-1
- https://ubuntu.com/security/notices/USN-7344-1
- https://ubuntu.com/security/notices/USN-7344-2
- https://ubuntu.com/security/notices/USN-7413-1
- https://www.cve.org/CVERecord?id=CVE-2024-43892