high CVSS 7.8

CVE-2022-48733·Kernel vulnerability

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.

Severity: high
Software: Kernel
Fixed in: 5.16.8
Published: 2024-06-20

Affected versions

From: 5.16

Until: 5.16.8

Fixed in: 5.16.8

How to fix this CVE

Update your Linux kernel to version 5.16.8 or later to resolve a use-after-free vulnerability in the Btrfs snapshot creation code. This vulnerability occurs when snapshot creation fails and improperly frees memory structures that remain referenced by active transactions. Apply the patch immediately to systems running vulnerable kernel versions 5.16.0 through 5.16.7.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

Run 'uname -r' to check your current kernel version. If it returns 5.16.0 through 5.16.7, your system is vulnerable.
Execute 'grep -i btrfs /proc/filesystems' to verify if Btrfs is enabled on your system; if present, snapshot functionality is available.
Search kernel logs with 'dmesg | grep -i "use.after.free\|btrfs\|snapshot"' for memory corruption or snapshot-related errors.
After patching, run 'uname -r' again to confirm the kernel version is 5.16.8 or later, then reboot if necessary.

FAQ

What is CVE-2022-48733?

CVE-2022-48733 is a use-after-free vulnerability in the Linux kernel's Btrfs filesystem implementation. When snapshot creation fails during a transaction commit, the pending snapshot structure is freed prematurely but remains attached to the transaction list, allowing concurrent operations to access freed memory.

Is CVE-2022-48733 being actively exploited?

No, CVE-2022-48733 is not listed in CISA's Known Exploited Vulnerabilities catalog and has no public exploit available. However, the high CVSS score (7.8) indicates significant risk if local attackers can trigger failed snapshot operations.

What versions of Kernel are affected by CVE-2022-48733?

Linux kernel versions 5.16.0 through 5.16.7 are affected. The vulnerability was fixed in version 5.16.8.

How do I check if my server is vulnerable to CVE-2022-48733?

Run 'uname -r' and check if the output is between 5.16.0 and 5.16.7. If so, your system is vulnerable. Also verify Btrfs is in use with 'grep btrfs /proc/filesystems' or 'df -T | grep btrfs'.

Does Defensia detect CVE-2022-48733?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2022-48733 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)

CVE-2024-39462CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: clk: bcm: dvp: Assign ->num before accessing ->hws Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by") annotated the hws member of 'struct clk_hw_onecell_data' with __counted_by, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in clk_dvp_probe() due to ->num being assigned after ->hws has been accessed: UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2 index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]') Move the ->num initialization to before the first access of ->hws, which clears up the warning.

CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.

CVE-2021-47378CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nvme-rdma: destroy cm id before destroy qp to avoid use after free We should always destroy cm_id before destroy qp to avoid to get cma event after qp was destroyed, which may lead to use after free. In RDMA connection establishment error flow, don't destroy qp in cm event handler.Just report cm_error to upper level, qp will be destroy in nvme_rdma_alloc_queue() after destroy cm id.

CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2022-48733. Free for 1 server.

Get started free