# CVE-2021-47200: linux: In the Linux kernel, the following vulnerability has been resolved:  drm/prime: Fix use after free in mmap with drm_g...

CVE-2021-47200 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47200, released April 10, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47200
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0022
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap  drm_gem_ttm_mmap() drops a reference to the gem object on success. If the gem object's refcount == 1 on entry to drm_gem_prime_mmap(), that drop will free the gem object, and the subsequent drm_gem_object_get() will be a UAF. Fix by grabbing a reference before calling the mmap helper.  This issue was forseen when the reference dropping was adding in commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"):   "For that to work properly the drm_gem_object_get() call in   drm_gem_ttm_mmap() must be moved so it happens before calling   obj->funcs->mmap(), otherwise the gem refcount would go down   to zero."

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.5-1 | [DEBIAN-CVE-2021-47200](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47200.md) | Apr 10, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.5-1 | [DEBIAN-CVE-2021-47200](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47200.md) | Apr 10, 2024 |
| Linux | linux Debian 14 | 5.15.5-1 | [DEBIAN-CVE-2021-47200](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47200.md) | Apr 10, 2024 |

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