CVE-2026-98324dmaengine: pxa: fix double counting of the hw descriptors

Official description

In the Linux kernel, the following vulnerability has been resolved: dmaengine: pxa: fix double counting of the hw descriptors pxad_alloc_desc() was converted from kzalloc(struct_size(sw_desc, hw_desc, nb_hw_desc), GFP_NOWAIT) to kzalloc_flex(), which sets the __counted_by() counter sw_desc->nb_desc itself - but only where the compiler has __builtin_counted_by_ref(), so from gcc 15.1 or clang 22.1 on. The loop below it still increments nb_desc, which makes it come out doubled there and correct elsewhere. nb_desc is what pxad_free_desc() iterates over and what set_updater_desc() indexes from, so set it explicitly and drop the increment. The error path has to lower it to the number of descriptors allocated so far, otherwise pxad_free_desc() would free entries that were never allocated.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1de93785f32b450e9eae1e4fcfb7d03eb49eb27e
• https://git.kernel.org/stable/c/f6504be006aa4bb4bd26285f410a885c17920d65