DEBIAN-CVE-2026-90012

In the Linux kernel, the following vulnerability has been resolved:  spi: Fix DMA mapping ownership on partial map failure  If RX mapping fails after TX mapping succeeds, spimapmsg() unmaps TX but leaves txsgmapped set. If TX mapping fails on a later transfer, mappings created for earlier transfers remain active.  In both cases, cur{tx,rx}dmadev have not yet been updated because they are assigned only after every transfer has been mapped. The subsequent spiunmapmsg() may therefore unmap the TX mapping again or release earlier mappings using a NULL or stale device. Using a NULL device can trigger an oops. An empty SG table does not prevent the NULL dereference because dmaunmapsgattrs() accesses the device before checking the entry count.  Publish both mapping devices before mapping starts and unwind all failures through spiunmapmsg(). This clears the mapping flags and releases each mapping once with the device that created it.  Publishing the devices before the loop also refreshes them when no transfer needs mapping. No mapping flag is set in that case, so current users do not use the pointers as mapping owners.