# CVE-2022-49753: dmaengine: Fix double increment of client_count in dma_chan_get()
> A double increment bug in the Linux kernel DMA engine causes reference count underflows, leading to use-after-free conditions and potential system crashes.
- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2025
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2022-49753, GHSA-c6c6-6xm6-jhp9, UBUNTU-CVE-2022-49753
## What is CVE-2022-49753?
CVE-2022-49753 is a high-severity use after free vulnerability in Linux kernel, published on 27 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.
### Official description
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(), 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]
[ 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]
[ 130.323081] ---[ end trace eff7156d56b5cf25 ]---
cat /sys/class/dma/dma0chan*/in_use would get the wrong result.
2
2
2
Test-by: Jie Hai
Weakness: CWE-416 (Use After Free)
## Which versions are affected by CVE-2022-49753?
It affects 1 product.
Products: Linux kernel.
## How do I fix CVE-2022-49753?
Apply the vendor's patch.
## Is CVE-2022-49753 being exploited?
There is no known exploitation of CVE-2022-49753 in the wild and no public exploit code.
## Other vulnerabilities in Linux kernel
- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)
## Fix prompt for AI coding agents
```text
Check this codebase for CVE-2022-49753 and fix it if it is affected.
What it is: CVE-2022-49753 is a high-severity use after free vulnerability in Linux kernel, published on 27 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2022-49753 in the wild and no public exploit code.
Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2022-49753/ (Markdown: https://insights.sbomify.com/CVE-2022-49753/index.md)
```
## Sources
- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49753
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49753
- OSV: https://osv.dev/vulnerability/CVE-2022-49753
---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49753/
Summaries are generated and may contain mistakes; the official description above is the record.