CVE-2026-46215

In the Linux kernel, the following vulnerability has been resolved:

drm: Set old handle to NULL before prime swap in change_handle

There was a potential race condition in change_handle. The ioctl briefly had a single object with two idr entries; a concurrent gem_close could delete the object and remove one of the handles while leaving the other one dangling, which could subsequently be dereferenced for a use-after-free.

To fix this, do the same dance that gem_close itself does. (f6cd7daecff5 drm: Release driver references to handle before making it available again) First idr_replace the old handle to NULL. Later, if the prime operations are successful, actually close it.

create_tail required a similar dance to avoid a similar problem. (bd46cece51a3 drm/gem: Fix race in drm_gem_handle_create_tail()) It idr_allocs the new handle with NULL, then swaps in the correct object later to avoid races. We dont need to do that here, since the only operations that could race are drm_prime, and change_handle holds the prime lock for the entire duration.

v2: cleanups of error paths

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/5e28b7b94408897e41c63477aabc9e1db439bc8c
• https://git.kernel.org/stable/c/61bd96d3e5472c253f9c1ab77608f0c8aaa9d025
• https://git.kernel.org/stable/c/672464dd53231509c9c771110798c56d4660e19e