UBUNTU-CVE-2022-48733
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix use-after-free after failure to create a snapshot At ioctl.c:create_snapshot(), we allocate a pending snapshot structure and then attach it to the transaction's list of pending snapshots. After that we call btrfs_commit_transaction(), and if that returns an error we jump to 'fail' label, where we kfree() the pending snapshot structure. This can result in a later use-after-free of the pending snapshot: 1) We allocated the pending snapshot and added it to the transaction's list of pending snapshots; 2) We call btrfs_commit_transaction(), and it fails either at the first call to btrfs_run_delayed_refs() or btrfs_start_dirty_block_groups(). In both cases, we don't abort the transaction and we release our transaction handle. We jump to the 'fail' label and free the pending snapshot structure. We return with the pending snapshot still in the transaction's list; 3) Another task commits the transaction. This time there's no error at all, and then during the transaction commit it accesses a pointer to the pending snapshot structure that the snapshot creation task has already freed, resulting in a user-after-free. This issue could actually be detected by smatch, which produced the following warning: fs/btrfs/ioctl.c:843 create_snapshot() warn: '&pending_snapshot->list' not removed from list So fix this by not having the snapshot creation ioctl directly add the pending snapshot to the transaction's list. Instead add the pending snapshot to the transaction handle, and then at btrfs_commit_transaction() we add the snapshot to the list only when we can guarantee that any error returned after that point will result in a transaction abort, in which case the ioctl code can safely free the pending snapshot and no one can access it anymore.
02 / AFFECTED SOFTWARE
Affected packages
1 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
6 explicit affected versions
69 explicit affected versions
191 explicit affected versions
7 explicit affected versions
96 explicit affected versions
66 explicit affected versions
35 explicit affected versions
18 explicit affected versions
97 explicit affected versions
98 explicit affected versions
13 explicit affected versions
4 explicit affected versions
23 explicit affected versions
102 explicit affected versions
1 explicit affected versions
1 explicit affected versions
21 explicit affected versions
16 explicit affected versions
10 explicit affected versions
53 explicit affected versions
7 explicit affected versions
12 explicit affected versions
12 explicit affected versions
1 explicit affected versions
7 explicit affected versions
86 explicit affected versions
12 explicit affected versions
101 explicit affected versions
109 explicit affected versions
12 explicit affected versions
97 explicit affected versions
10 explicit affected versions
168 explicit affected versions
37 explicit affected versions
101 explicit affected versions
10 explicit affected versions
1 explicit affected versions
36 explicit affected versions
26 explicit affected versions
13 explicit affected versions
1 explicit affected versions
29 explicit affected versions
89 explicit affected versions
13 explicit affected versions
1 explicit affected versions
84 explicit affected versions
101 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
95 explicit affected versions
11 explicit affected versions
12 explicit affected versions
118 explicit affected versions
7 explicit affected versions
12 explicit affected versions
99 explicit affected versions
2 explicit affected versions
111 explicit affected versions
131 explicit affected versions
10 explicit affected versions
26 explicit affected versions
35 explicit affected versions
13 explicit affected versions
118 explicit affected versions
59 explicit affected versions
16 explicit affected versions
3 explicit affected versions
72 explicit affected versions
1 explicit affected versions
66 explicit affected versions
51 explicit affected versions
71 explicit affected versions
12 explicit affected versions
27 explicit affected versions
1 explicit affected versions
1 explicit affected versions
75 explicit affected versions
8 explicit affected versions
5 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
88 explicit affected versions
13 explicit affected versions
53 explicit affected versions
7 explicit affected versions
73 explicit affected versions
10 explicit affected versions
12 explicit affected versions
88 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
38 explicit affected versions
9 explicit affected versions
11 explicit affected versions
145 explicit affected versions
7 explicit affected versions
78 explicit affected versions
60 explicit affected versions
122 explicit affected versions
101 explicit affected versions
4 explicit affected versions
94 explicit affected versions
43 explicit affected versions
54 explicit affected versions
125 explicit affected versions
145 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
89 explicit affected versions
4 explicit affected versions
78 explicit affected versions
1 explicit affected versions
48 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix use-after-free after failure to create a snapshot At ioctl.c:create_snapshot(), we allocate a pending snapshot structure and then attach it to the transaction's list of pending snapshots. After that we call btrfs_commit_transaction(), and if that returns an error we jump to 'fail' label, where we kfree() the pending snapshot structure. This can result in a later use-after-free of the pending snapshot: 1) We allocated the pending snapshot and added it to the transaction's list of pending snapshots; 2) We call btrfs_commit_transaction(), and it fails either at the first call to btrfs_run_delayed_refs() or btrfs_start_dirty_block_groups(). In both cases, we don't abort the transaction and we release our transaction handle. We jump to the 'fail' label and free the pending snapshot structure. We return with the pending snapshot still in the transaction's list; 3) Another task commits the transaction. This time there's no error at all, and then during the transaction commit it accesses a pointer to the pending snapshot structure that the snapshot creation task has already freed, resulting in a user-after-free. This issue could actually be detected by smatch, which produced the following warning: fs/btrfs/ioctl.c:843 create_snapshot() warn: '&pending_snapshot->list' not removed from list So fix this by not having the snapshot creation ioctl directly add the pending snapshot to the transaction's list. Instead add the pending snapshot to the transaction handle, and then at btrfs_commit_transaction() we add the snapshot to the list only when we can guarantee that any error returned after that point will result in a transaction abort, in which case the ioctl code can safely free the pending snapshot and no one can access it anymore.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/28b21c558a3753171097193b6f6602a94169093a
- https://git.kernel.org/stable/c/28b21c558a3753171097193b6f6602a94169093a
- https://git.kernel.org/stable/c/9372fa1d73da5f1673921e365d0cd2c27ec7adc2
- https://git.kernel.org/stable/c/a7b717fa15165d3d9245614680bebc48a52ac05d
- https://ubuntu.com/security/CVE-2022-48733
- https://ubuntu.com/security/notices/USN-7121-1
- https://ubuntu.com/security/notices/USN-7121-2
- https://ubuntu.com/security/notices/USN-7121-3
- https://ubuntu.com/security/notices/USN-7148-1
- https://ubuntu.com/security/notices/USN-7159-1
- https://ubuntu.com/security/notices/USN-7159-2
- https://ubuntu.com/security/notices/USN-7159-3
- https://ubuntu.com/security/notices/USN-7159-4
- https://ubuntu.com/security/notices/USN-7159-5
- https://ubuntu.com/security/notices/USN-7195-1
- https://ubuntu.com/security/notices/USN-7195-2
- https://www.cve.org/CVERecord?id=CVE-2022-48733