UBUNTU-CVE-2021-47119
In the Linux kernel, the following vulnerability has been resolved: ext4: fix memory leak in ext4_fill_super Buffer head references must be released before calling kill_bdev(); otherwise the buffer head (and its page referenced by b_data) will not be freed by kill_bdev, and subsequently that bh will be leaked. If blocksizes differ, sb_set_blocksize() will kill current buffers and page cache by using kill_bdev(). And then super block will be reread again but using correct blocksize this time. sb_set_blocksize() didn't fully free superblock page and buffer head, and being busy, they were not freed and instead leaked. This can easily be reproduced by calling an infinite loop of: systemctl start <ext4_on_lvm>.mount, and systemctl stop <ext4_on_lvm>.mount ... since systemd creates a cgroup for each slice which it mounts, and the bh leak get amplified by a dying memory cgroup that also never gets freed, and memory consumption is much more easily noticed.
02 / AFFECTED SOFTWARE
Affected packages
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
6 explicit affected versions
74 explicit affected versions
180 explicit affected versions
7 explicit affected versions
102 explicit affected versions
70 explicit affected versions
35 explicit affected versions
18 explicit affected versions
101 explicit affected versions
104 explicit affected versions
13 explicit affected versions
4 explicit affected versions
23 explicit affected versions
106 explicit affected versions
1 explicit affected versions
1 explicit affected versions
21 explicit affected versions
16 explicit affected versions
10 explicit affected versions
58 explicit affected versions
7 explicit affected versions
12 explicit affected versions
12 explicit affected versions
1 explicit affected versions
7 explicit affected versions
91 explicit affected versions
12 explicit affected versions
107 explicit affected versions
115 explicit affected versions
12 explicit affected versions
102 explicit affected versions
105 explicit affected versions
10 explicit affected versions
173 explicit affected versions
37 explicit affected versions
10 explicit affected versions
1 explicit affected versions
38 explicit affected versions
26 explicit affected versions
13 explicit affected versions
1 explicit affected versions
29 explicit affected versions
94 explicit affected versions
13 explicit affected versions
1 explicit affected versions
87 explicit affected versions
106 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
99 explicit affected versions
11 explicit affected versions
12 explicit affected versions
122 explicit affected versions
7 explicit affected versions
12 explicit affected versions
105 explicit affected versions
2 explicit affected versions
115 explicit affected versions
150 explicit affected versions
136 explicit affected versions
10 explicit affected versions
26 explicit affected versions
40 explicit affected versions
13 explicit affected versions
122 explicit affected versions
63 explicit affected versions
16 explicit affected versions
3 explicit affected versions
76 explicit affected versions
1 explicit affected versions
72 explicit affected versions
51 explicit affected versions
75 explicit affected versions
12 explicit affected versions
27 explicit affected versions
1 explicit affected versions
1 explicit affected versions
80 explicit affected versions
8 explicit affected versions
5 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
94 explicit affected versions
13 explicit affected versions
58 explicit affected versions
7 explicit affected versions
77 explicit affected versions
10 explicit affected versions
12 explicit affected versions
92 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
7 explicit affected versions
83 explicit affected versions
66 explicit affected versions
126 explicit affected versions
105 explicit affected versions
4 explicit affected versions
98 explicit affected versions
43 explicit affected versions
60 explicit affected versions
129 explicit affected versions
150 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
92 explicit affected versions
4 explicit affected versions
78 explicit affected versions
1 explicit affected versions
52 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: ext4: fix memory leak in ext4_fill_super Buffer head references must be released before calling kill_bdev(); otherwise the buffer head (and its page referenced by b_data) will not be freed by kill_bdev, and subsequently that bh will be leaked. If blocksizes differ, sb_set_blocksize() will kill current buffers and page cache by using kill_bdev(). And then super block will be reread again but using correct blocksize this time. sb_set_blocksize() didn't fully free superblock page and buffer head, and being busy, they were not freed and instead leaked. This can easily be reproduced by calling an infinite loop of: systemctl start <ext4_on_lvm>.mount, and systemctl stop <ext4_on_lvm>.mount ... since systemd creates a cgroup for each slice which it mounts, and the bh leak get amplified by a dying memory cgroup that also never gets freed, and memory consumption is much more easily noticed.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/afd09b617db3786b6ef3dc43e28fe728cfea84df
- https://git.kernel.org/stable/c/01d349a481f0591230300a9171330136f9159bcd
- https://git.kernel.org/stable/c/1385b23396d511d5233b8b921ac3058b3f86a5e1
- https://git.kernel.org/stable/c/afd09b617db3786b6ef3dc43e28fe728cfea84df
- https://ubuntu.com/security/CVE-2021-47119
- https://ubuntu.com/security/notices/USN-7415-1
- https://ubuntu.com/security/notices/USN-7428-1
- https://ubuntu.com/security/notices/USN-7428-2
- https://ubuntu.com/security/notices/USN-7429-1
- https://ubuntu.com/security/notices/USN-7429-2
- https://ubuntu.com/security/notices/USN-7461-1
- https://ubuntu.com/security/notices/USN-7461-2
- https://ubuntu.com/security/notices/USN-7461-3
- https://ubuntu.com/security/notices/USN-7462-1
- https://ubuntu.com/security/notices/USN-7462-2
- https://ubuntu.com/security/notices/USN-7463-1
- https://ubuntu.com/security/notices/USN-7539-1
- https://ubuntu.com/security/notices/USN-7540-1
- https://www.cve.org/CVERecord?id=CVE-2021-47119