Linux Kernel up to 5.18.12 parse_var_defs double free

Summaryinfo

A vulnerability has been found in Linux Kernel up to 4.19.252/5.4.206/5.10.131/5.15.55/5.18.12 and classified as critical. This vulnerability affects the function parse_var_defs. This manipulation causes double free. This vulnerability appears as CVE-2022-49648. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 4.19.252/5.4.206/5.10.131/5.15.55/5.18.12. It has been declared as critical. Affected by this vulnerability is the function parse_var_defs. The manipulation with an unknown input leads to a double free vulnerability. The CWE definition for the vulnerability is CWE-415. The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: tracing/histograms: Fix memory leak problem This reverts commit 46bbe5c671e06f070428b9be142cc4ee5cedebac. As commit 46bbe5c671e0 ("tracing: fix double free") said, the "double free" problem reported by clang static analyzer is: > In parse_var_defs() if there is a problem allocating > var_defs.expr, the earlier var_defs.name is freed. > This free is duplicated by free_var_defs() which frees > the rest of the list. However, if there is a problem allocating N-th var_defs.expr: + in parse_var_defs(), the freed 'earlier var_defs.name' is actually the N-th var_defs.name; + then in free_var_defs(), the names from 0th to (N-1)-th are freed; IF ALLOCATING PROBLEM HAPPENED HERE!!! -+ \ | 0th 1th (N-1)-th N-th V +-------------+-------------+-----+-------------+----------- var_defs: | name | expr | name | expr | ... | name | expr | name | /// +-------------+-------------+-----+-------------+----------- These two frees don't act on same name, so there was no "double free" problem before. Conversely, after that commit, we get a "memory leak" problem because the above "N-th var_defs.name" is not freed. If enable CONFIG_DEBUG_KMEMLEAK and inject a fault at where the N-th var_defs.expr allocated, then execute on shell like: $ echo 'hist:key=call_site:val=$v1,$v2:v1=bytes_req,v2=bytes_alloc' > \ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger Then kmemleak reports: unreferenced object 0xffff8fb100ef3518 (size 8): comm "bash", pid 196, jiffies 4295681690 (age 28.538s) hex dump (first 8 bytes): 76 31 00 00 b1 8f ff ff v1...... backtrace: [] kstrdup+0x2d/0x60 [] event_hist_trigger_parse+0x206f/0x20e0 [] trigger_process_regex+0xc0/0x110 [] event_trigger_write+0x75/0xd0 [] vfs_write+0xbb/0x2a0 [] ksys_write+0x59/0xd0 [] do_syscall_64+0x3a/0x80 [] entry_SYSCALL_64_after_hwframe+0x46/0xb0

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2022-49648 since 02/26/2025. The exploitation appears to be difficult. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/27/2025).

The vulnerability scanner Nessus provides a plugin with the ID 237260 (CentOS 9 : kernel-5.14.0-587.el9), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.19.253, 5.4.207, 5.10.132, 5.15.56 or 5.18.13 eliminates this vulnerability. Applying the patch eb622d5580b9e2ff694f62da6410618bd73853cb/ecc6dec12c33aa92c086cd702af9f544ddaf3c75/78a1400c42ee11197eb1f0f85ba51df9a4fdfff0/22eeff55679d9e7c0f768c79bfbd83e2f8142d89/4d453eb5e1eec89971aa5b3262857ee26cfdffd3/7edc3945bdce9c39198a10d6129377a5c53559c2 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (237260). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 4.19.252
• 5.4.206
• 5.10.131
• 5.15.0
• 5.15.1
• 5.15.2
• 5.15.3
• 5.15.4
• 5.15.5
• 5.15.6
• 5.15.7
• 5.15.8
• 5.15.9
• 5.15.10
• 5.15.11
• 5.15.12
• 5.15.13
• 5.15.14
• 5.15.15
• 5.15.16
• 5.15.17
• 5.15.18
• 5.15.19
• 5.15.20
• 5.15.21
• 5.15.22
• 5.15.23
• 5.15.24
• 5.15.25
• 5.15.26
• 5.15.27
• 5.15.28
• 5.15.29
• 5.15.30
• 5.15.31
• 5.15.32
• 5.15.33
• 5.15.34
• 5.15.35
• 5.15.36
• 5.15.37
• 5.15.38
• 5.15.39
• 5.15.40
• 5.15.41
• 5.15.42
• 5.15.43
• 5.15.44
• 5.15.45
• 5.15.46
• 5.15.47
• 5.15.48
• 5.15.49
• 5.15.50
• 5.15.51
• 5.15.52
• 5.15.53
• 5.15.54
• 5.15.55
• 5.18.0
• 5.18.1
• 5.18.2
• 5.18.3
• 5.18.4
• 5.18.5
• 5.18.6
• 5.18.7
• 5.18.8
• 5.18.9
• 5.18.10
• 5.18.11
• 5.18.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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