Bug 2297554 (CVE-2024-40970)

Summary: CVE-2024-40970 kernel: Avoid hw_desc array overrun in dw-axi-dmac
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: kernel 5.15.162, kernel 6.1.96, kernel 6.6.36, kernel 6.9.7, kernel 6.10-rc1 Doc Type: If docs needed, set a value
Doc Text:
A vulnerability was found in `dw-axi-dmac` in the Linux kernel and has been resolved to prevent an overrun of the `hw_desc` array. This issue occurred when using three descriptors, each comprising three segments, resulting in nine allocated descriptors.
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Description OSIDB Bzimport 2024-07-12 13:43:13 UTC 
In the Linux kernel, the following vulnerability has been resolved:

Avoid hw_desc array overrun in dw-axi-dmac

I have a use case where nr_buffers = 3 and in which each descriptor is composed by 3
segments, resulting in the DMA channel descs_allocated to be 9. Since axi_desc_put()
handles the hw_desc considering the descs_allocated, this scenario would result in a
kernel panic (hw_desc array will be overrun).

To fix this, the proposal is to add a new member to the axi_dma_desc structure,
where we keep the number of allocated hw_descs (axi_desc_alloc()) and use it in
axi_desc_put() to handle the hw_desc array correctly.

Additionally I propose to remove the axi_chan_start_first_queued() call after completing
the transfer, since it was identified that unbalance can occur (started descriptors can
be interrupted and transfer ignored due to DMA channel not being enabled).