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** Changed in: linux (Ubuntu)
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1877070
Title:
kmalloc-192 slab corruption inside VM with QXL driver
Status in linux package in Ubuntu:
Incomplete
Bug description:
I would like to ask to backport following patch into ubuntu kernels:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=933db73351d359f74b14f4af095808260aff11f9
This bug silently corrupts memory in kmalloc-192 objects.
we observed several such cases and have few crashes inside RHEL7/8 VMs with
QXL driver.
during investigation we have found that the problem exist in mainline.
Some details:
qxl driver inside guest submit command with reference to allocated struct
qxl_release.
Host handles it, moves related struct qxl_release to release_ring and trigger
interrupt
guest handles interrupt and forces gabage collector in qxl driver
which wolks through release_ring and removes qxl_release structures.
and then main thread calls qxl_release_fence_buffer_objects() it access
already freed qxl_release.
Solution is to swap the qxl_release_fence_buffer_objects() +
qxl_push_{cursor,command}_ring_release() calls.
I would note -- direct cherry-pick can be incomplete,
old kernels can have few other places where
qxl_release_fence_buffer_objects() is called after
qxl_push_{cursor,command}_ring_release().
All such places should be fixed, I did it for 4.4, 4.9 and few other stable
kernels.
We did not have confirmed cases for ubuntu inside VM,
however we believe your kernels should be affected too.
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