CVE-2022-49753
Published: 27 March 2025
Summary
CVE-2022-49753 is a high-severity Use After Free (CWE-416) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 0.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2022-49753 is a use-after-free vulnerability (CWE-416) in the Linux kernel's dmaengine subsystem, stemming from a double increment of the client_count in the dma_chan_get() function for public DMA channels. The initial increment occurs in balance_ref_count(), followed by another before the function returns, resulting in an incorrect reference count. This prevents proper freeing of channel resources upon client release, as demonstrated by a kref underflow warning during repeated load and unload of the async_tx module on a Dell PowerEdge R7425 server running kernel 5.14.0-185.el9.x86_64. Additionally, querying /sys/class/dma/dma0chan*/in_use yields incorrect results, such as repeated values of 2.
A local attacker with low privileges (AV:L/AC:L/PR:L/UI:N) can exploit this vulnerability to achieve high confidentiality, integrity, and availability impacts (CVSS 3.1 score of 7.8), potentially triggering use-after-free conditions. Exploitation manifests during operations like module unloading (e.g., via modprobe on async_tx), leading to refcount underflow and warnings from refcount_warn_saturate() in lib/refcount.c, as shown in the provided kernel trace involving dma_chan_put() and dmaengine_put().
Mitigation involves applying upstream patches from the Linux kernel stable repository, including commits such as 142d644fd2cc059ffa042fbfb68e766433ef3afd, 18dd3b30d4c7e8440c63118c7a7b687372b9567f, 1b409e14b4b7af034e0450f95c165b6c5c87dbc1, 42ecd72f02cd657b00b559621e7ef7d2c4d3e5f1, and 71c601965532c38030133535f7cd93c1efa75af1, which correct the double increment issue.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2022-55170
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: dmaengine: Fix double increment of client_count in dma_chan_get() The first time dma_chan_get() is called for a channel the channel client_count is incorrectly incremented twice for public channels, first in balance_ref_count(),…
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and again prior to returning. This results in an incorrect client count which will lead to the channel resources not being freed when they should be. A simple test of repeated module load and unload of async_tx on a Dell Power Edge R7425 also shows this resulting in a kref underflow warning. [ 124.329662] async_tx: api initialized (async) [ 129.000627] async_tx: api initialized (async) [ 130.047839] ------------[ cut here ]------------ [ 130.052472] refcount_t: underflow; use-after-free. [ 130.057279] WARNING: CPU: 3 PID: 19364 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x110 [ 130.065811] Modules linked in: async_tx(-) rfkill intel_rapl_msr intel_rapl_common amd64_edac edac_mce_amd ipmi_ssif kvm_amd dcdbas kvm mgag200 drm_shmem_helper acpi_ipmi irqbypass drm_kms_helper ipmi_si syscopyarea sysfillrect rapl pcspkr ipmi_devintf sysimgblt fb_sys_fops k10temp i2c_piix4 ipmi_msghandler acpi_power_meter acpi_cpufreq vfat fat drm fuse xfs libcrc32c sd_mod t10_pi sg ahci crct10dif_pclmul libahci crc32_pclmul crc32c_intel ghash_clmulni_intel igb megaraid_sas i40e libata i2c_algo_bit ccp sp5100_tco dca dm_mirror dm_region_hash dm_log dm_mod [last unloaded: async_tx] [ 130.117361] CPU: 3 PID: 19364 Comm: modprobe Kdump: loaded Not tainted 5.14.0-185.el9.x86_64 #1 [ 130.126091] Hardware name: Dell Inc. PowerEdge R7425/02MJ3T, BIOS 1.18.0 01/17/2022 [ 130.133806] RIP: 0010:refcount_warn_saturate+0xba/0x110 [ 130.139041] Code: 01 01 e8 6d bd 55 00 0f 0b e9 72 9d 8a 00 80 3d 26 18 9c 01 00 75 85 48 c7 c7 f8 a3 03 9d c6 05 16 18 9c 01 01 e8 4a bd 55 00 <0f> 0b e9 4f 9d 8a 00 80 3d 01 18 9c 01 00 0f 85 5e ff ff ff 48 c7 [ 130.157807] RSP: 0018:ffffbf98898afe68 EFLAGS: 00010286 [ 130.163036] RAX: 0000000000000000 RBX: ffff9da06028e598 RCX: 0000000000000000 [ 130.170172] RDX: ffff9daf9de26480 RSI: ffff9daf9de198a0 RDI: ffff9daf9de198a0 [ 130.177316] RBP: ffff9da7cddf3970 R08: 0000000000000000 R09: 00000000ffff7fff [ 130.184459] R10: ffffbf98898afd00 R11: ffffffff9d9e8c28 R12: ffff9da7cddf1970 [ 130.191596] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 130.198739] FS: 00007f646435c740(0000) GS:ffff9daf9de00000(0000) knlGS:0000000000000000 [ 130.206832] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 130.212586] CR2: 00007f6463b214f0 CR3: 00000008ab98c000 CR4: 00000000003506e0 [ 130.219729] Call Trace: [ 130.222192] <TASK> [ 130.224305] dma_chan_put+0x10d/0x110 [ 130.227988] dmaengine_put+0x7a/0xa0 [ 130.231575] __do_sys_delete_module.constprop.0+0x178/0x280 [ 130.237157] ? syscall_trace_enter.constprop.0+0x145/0x1d0 [ 130.242652] do_syscall_64+0x5c/0x90 [ 130.246240] ? exc_page_fault+0x62/0x150 [ 130.250178] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 130.255243] RIP: 0033:0x7f6463a3f5ab [ 130.258830] Code: 73 01 c3 48 8b 0d 75 a8 1b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 45 a8 1b 00 f7 d8 64 89 01 48 [ 130.277591] RSP: 002b:00007fff22f972c8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0 [ 130.285164] RAX: ffffffffffffffda RBX: 000055b6786edd40 RCX: 00007f6463a3f5ab [ 130.292303] RDX: 0000000000000000 RSI: 0000000000000800 RDI: 000055b6786edda8 [ 130.299443] RBP: 000055b6786edd40 R08: 0000000000000000 R09: 0000000000000000 [ 130.306584] R10: 00007f6463b9eac0 R11: 0000000000000206 R12: 000055b6786edda8 [ 130.313731] R13: 0000000000000000 R14: 000055b6786edda8 R15: 00007fff22f995f8 [ 130.320875] </TASK> [ 130.323081] ---[ end trace eff7156d56b5cf25 ]--- cat /sys/class/dma/dma0chan*/in_use would get the wrong result. 2 2 2 Test-by: Jie Hai <haijie1@huawei.com>
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in Linux kernel dmaengine subsystem enables local privilege escalation via exploitation of the reference count bug.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely remediation of identified flaws like the double client_count increment in dma_chan_get() via kernel patches to prevent use-after-free and resource leaks.
Enables vulnerability scanning to identify CVE-2022-49753 in Linux kernel versions, such as 5.14.0-185.el9.x86_64, affected by the dmaengine reference counting bug.
Monitors integrity of kernel software and modules to detect alterations or unpatched states leading to incorrect client counts and kref underflows during module operations.