UBUNTU-CVE-2025-21737
In the Linux kernel, the following vulnerability has been resolved: ceph: fix memory leak in ceph_mds_auth_match() We now free the temporary target path substring allocation on every possible branch, instead of omitting the default branch. In some cases, a memory leak occured, which could rapidly crash the system (depending on how many file accesses were attempted). This was detected in production because it caused a continuous memory growth, eventually triggering kernel OOM and completely hard-locking the kernel. Relevant kmemleak stacktrace: unreferenced object 0xffff888131e69900 (size 128): comm "git", pid 66104, jiffies 4295435999 hex dump (first 32 bytes): 76 6f 6c 75 6d 65 73 2f 63 6f 6e 74 61 69 6e 65 volumes/containe 72 73 2f 67 69 74 65 61 2f 67 69 74 65 61 2f 67 rs/gitea/gitea/g backtrace (crc 2f3bb450): [<ffffffffaa68fb49>] __kmalloc_noprof+0x359/0x510 [<ffffffffc32bf1df>] ceph_mds_check_access+0x5bf/0x14e0 [ceph] [<ffffffffc3235722>] ceph_open+0x312/0xd80 [ceph] [<ffffffffaa7dd786>] do_dentry_open+0x456/0x1120 [<ffffffffaa7e3729>] vfs_open+0x79/0x360 [<ffffffffaa832875>] path_openat+0x1de5/0x4390 [<ffffffffaa834fcc>] do_filp_open+0x19c/0x3c0 [<ffffffffaa7e44a1>] do_sys_openat2+0x141/0x180 [<ffffffffaa7e4945>] __x64_sys_open+0xe5/0x1a0 [<ffffffffac2cc2f7>] do_syscall_64+0xb7/0x210 [<ffffffffac400130>] entry_SYSCALL_64_after_hwframe+0x77/0x7f It can be triggered by mouting a subdirectory of a CephFS filesystem, and then trying to access files on this subdirectory with an auth token using a path-scoped capability: $ ceph auth get client.services [client.services] key = REDACTED caps mds = "allow rw fsname=cephfs path=/volumes/" caps mon = "allow r fsname=cephfs" caps osd = "allow rw tag cephfs data=cephfs" $ cat /proc/self/mounts services@[REDACTED].cephfs=/volumes/containers /ceph/containers ceph rw,noatime,name=services,secret=<hidden>,ms_mode=prefer-crc,mount_timeout=300,acl,mon_addr=[REDACTED]:3300,recover_session=clean 0 0 $ seq 1 1000000 | xargs -P32 --replace={} touch /ceph/containers/file-{} && \ seq 1 1000000 | xargs -P32 --replace={} cat /ceph/containers/file-{} [ idryomov: combine if statements, rename rc to path_matched and make it a bool, formatting ]
02 / AFFECTED SOFTWARE
Affected packages
37 explicit affected versions
29 explicit affected versions
10 explicit affected versions
11 explicit affected versions
1 explicit affected versions
10 explicit affected versions
7 explicit affected versions
26 explicit affected versions
4 explicit affected versions
37 explicit affected versions
10 explicit affected versions
13 explicit affected versions
13 explicit affected versions
78 explicit affected versions
45 explicit affected versions
8 explicit affected versions
4 explicit affected versions
8 explicit affected versions
19 explicit affected versions
23 explicit affected versions
7 explicit affected versions
10 explicit affected versions
3 explicit affected versions
33 explicit affected versions
16 explicit affected versions
13 explicit affected versions
6 explicit affected versions
12 explicit affected versions
38 explicit affected versions
51 explicit affected versions
13 explicit affected versions
10 explicit affected versions
13 explicit affected versions
10 explicit affected versions
13 explicit affected versions
1 explicit affected versions
12 explicit affected versions
10 explicit affected versions
10 explicit affected versions
1 explicit affected versions
8 explicit affected versions
13 explicit affected versions
21 explicit affected versions
13 explicit affected versions
12 explicit affected versions
7 explicit affected versions
14 explicit affected versions
12 explicit affected versions
26 explicit affected versions
23 explicit affected versions
14 explicit affected versions
5 explicit affected versions
5 explicit affected versions
3 explicit affected versions
26 explicit affected versions
12 explicit affected versions
44 explicit affected versions
4 explicit affected versions
4 explicit affected versions
4 explicit affected versions
16 explicit affected versions
9 explicit affected versions
10 explicit affected versions
4 explicit affected versions
13 explicit affected versions
7 explicit affected versions
13 explicit affected versions
7 explicit affected versions
14 explicit affected versions
18 explicit affected versions
3 explicit affected versions
16 explicit affected versions
43 explicit affected versions
11 explicit affected versions
35 explicit affected versions
12 explicit affected versions
13 explicit affected versions
6 explicit affected versions
12 explicit affected versions
50 explicit affected versions
11 explicit affected versions
12 explicit affected versions
27 explicit affected versions
12 explicit affected versions
7 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: ceph: fix memory leak in ceph_mds_auth_match() We now free the temporary target path substring allocation on every possible branch, instead of omitting the default branch. In some cases, a memory leak occured, which could rapidly crash the system (depending on how many file accesses were attempted). This was detected in production because it caused a continuous memory growth, eventually triggering kernel OOM and completely hard-locking the kernel. Relevant kmemleak stacktrace: unreferenced object 0xffff888131e69900 (size 128): comm "git", pid 66104, jiffies 4295435999 hex dump (first 32 bytes): 76 6f 6c 75 6d 65 73 2f 63 6f 6e 74 61 69 6e 65 volumes/containe 72 73 2f 67 69 74 65 61 2f 67 69 74 65 61 2f 67 rs/gitea/gitea/g backtrace (crc 2f3bb450): [<ffffffffaa68fb49>] __kmalloc_noprof+0x359/0x510 [<ffffffffc32bf1df>] ceph_mds_check_access+0x5bf/0x14e0 [ceph] [<ffffffffc3235722>] ceph_open+0x312/0xd80 [ceph] [<ffffffffaa7dd786>] do_dentry_open+0x456/0x1120 [<ffffffffaa7e3729>] vfs_open+0x79/0x360 [<ffffffffaa832875>] path_openat+0x1de5/0x4390 [<ffffffffaa834fcc>] do_filp_open+0x19c/0x3c0 [<ffffffffaa7e44a1>] do_sys_openat2+0x141/0x180 [<ffffffffaa7e4945>] __x64_sys_open+0xe5/0x1a0 [<ffffffffac2cc2f7>] do_syscall_64+0xb7/0x210 [<ffffffffac400130>] entry_SYSCALL_64_after_hwframe+0x77/0x7f It can be triggered by mouting a subdirectory of a CephFS filesystem, and then trying to access files on this subdirectory with an auth token using a path-scoped capability: $ ceph auth get client.services [client.services] key = REDACTED caps mds = "allow rw fsname=cephfs path=/volumes/" caps mon = "allow r fsname=cephfs" caps osd = "allow rw tag cephfs data=cephfs" $ cat /proc/self/mounts services@[REDACTED].cephfs=/volumes/containers /ceph/containers ceph rw,noatime,name=services,secret=<hidden>,ms_mode=prefer-crc,mount_timeout=300,acl,mon_addr=[REDACTED]:3300,recover_session=clean 0 0 $ seq 1 1000000 | xargs -P32 --replace={} touch /ceph/containers/file-{} && \ seq 1 1000000 | xargs -P32 --replace={} cat /ceph/containers/file-{} [ idryomov: combine if statements, rename rc to path_matched and make it a bool, formatting ]
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/3b7d93db450e9d8ead80d75e2a303248f1528c35
- https://git.kernel.org/stable/c/146109fe936ac07f8f60cd6267543688985b96bc
- https://git.kernel.org/stable/c/2b6086c5efe5c7bd6e0eb440d96c26ca0d20d9d7
- https://git.kernel.org/stable/c/3b7d93db450e9d8ead80d75e2a303248f1528c35
- https://ubuntu.com/security/CVE-2025-21737
- https://ubuntu.com/security/notices/USN-7521-1
- https://ubuntu.com/security/notices/USN-7521-2
- https://ubuntu.com/security/notices/USN-7521-3
- https://www.cve.org/CVERecord?id=CVE-2025-21737