drm/gem: Try to fix change_handle ioctl, attempt 4

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Summary

CVECVE-2026-53145
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-25 09:16:31 UTC
Updated2026-06-25 09:16:31 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: drm/gem: Try to fix change_handle ioctl, attempt 4 [airlied: just added some comments on how to reenable] On-list because the cat is out of the bag and we're clearly not good enough to figure this out in private. The story thus far: 5e28b7b94408 ("drm: Set old handle to NULL before prime swap in change_handle") tried to fix a race condition between the gem_close and gem_change_handle ioctls, but got a few things wrong: - There's a confusion with the local variable handle, which is actually the new handle, and so the two-stage trick was actually applied to the wrong idr slot. 7164d78559b0 ("drm/gem: fix race between change_handle and handle_delete") tried to fix that by adding yet another code block, but forgot to add the error handling. Which meant we now have two paths, both kinda wrong. - dc366607c41c ("drm: Replace old pointer to new idr") tried to apply another fix, but inconsistently, again because of the handle confusion - this would be the right fix (kinda, somewhat, it's a mess) if we'd do the two-stage approach for the new handle. Except that wasn't the intent of the original fix. We also didn't have an igt merged for the original ioctl, which is a big no-go. This was attempted to address off-list in the original bugfix, and amd QA people claimed the bug was fixed now. Very clearly that's not the case. Here's my attempt to sort this out: - Rename the local variable to new_handle, the old aliasing with args->handle is just too dangerously confusing. - Merge the gem obj lookup with the two-stage idr_replace so that we avoid getting ourselves confused there. - This means we don't have a surplus temporary reference anymore, only an inherited from the idr. A concurrent gem_close on the new_handle could steal that. Fix that with the same two-stage approach create_tail uses. This is a bit overkill as documented in the comment, but I also don't trust my ability to understand this all correctly, so go with the established pattern we have from other ioctls instead for maximum paranoia. - Adjust error paths. I've tried to make the error and success paths common, because they are identical except for which handle is removed and on which we call idr_replace to (re)install the object again. But that made things messier to read, so I've left it at the more verbose version, which unfortunately hides the symmetry in the entire code flow a bit. - While at it, also replace the 7 space indent with 1 tab. And finally, because I flat out don't trust my abilities here at all anymore: - Disable the ioctl until we have the igt situation and everything else sorted out on-list and with full consensus. v2: Sashiko noticed that I didn't handle the error path for idr_replace correctly, it must be checked with IS_ERR_OR_NULL like in gem_handle_delete. So yeah, definitely should just the existing paths 1:1 because this is endless amounts of tricky. Also add the Fixes: line for the original ioctl, I forgot that too.

Risk And Classification

EPSS: 0.001730000 probability, percentile 0.070190000 (date 2026-06-27)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 672464dd53231509c9c771110798c56d4660e19e c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd git Not specified
CNA Linux Linux affected 61bd96d3e5472c253f9c1ab77608f0c8aaa9d025 1d9b93df7fc768228906e24220591ec1cddad391 git Not specified
CNA Linux Linux affected 5e28b7b94408897e41c63477aabc9e1db439bc8c 1a4f03d22fb655e5f192244fb2c87d8066fcfca2 git Not specified
CNA Linux Linux affected 318b995cffcfcaa69a234d28123a3f4ae186a9df git Not specified
CNA Linux Linux affected 38f12d0e10d83b66fa1466400d876a3a8da31542 git Not specified
CNA Linux Linux affected 0dfa42cfe4dbe114533480503934f43e33c1e83d git Not specified
CNA Linux Linux affected cde2c9257cbe8463b9dcf7b1075177b72b5fd938 git Not specified
CNA Linux Linux affected 6.18.32 6.18.36 semver Not specified
CNA Linux Linux affected 7.0.9 7.0.13 semver Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1a4f03d22fb655e5f192244fb2c87d8066fcfca2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c0639ede2f24ac224b2079cd35ecd5fd8ad4e3cd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1d9b93df7fc768228906e24220591ec1cddad391 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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