Linux Kernel EUVD-2026-32472

zram is a Linux kernel block device driver (drivers/block/zram/) that uses compressed RAM as storage, commonly deployed as a swap backend on memory-constrained systems. The Linux block I/O (bio) subsystem mandates that every bio submitted via submit_bio() must eventually be completed by a call to bio_endio(), signaling the submitter that the operation is done. In the affected code path, when zram receives a discard request whose granularity does not align to a full page (e.g., PAGESIZE=65536, discard step=4096), it detects the unsupported partial discard and returns early - but bypasses the end_bio label responsible for calling bio_endio(). This violates the bio lifecycle contract, causing any caller blocked in submit_bio_wait() to sleep indefinitely. The root cause is effectively an improper resource shutdown (analogous to CWE-404), where a cleanup/completion callback is missing on an early-exit code path. Affected products are identified by CPE cpe:2.3:o:linux:linux_kernel covering all versions from the introducing commit 0120dd6e4e202e19a0e011e486fb2da40a5ea279 up to the respective fix commits per stable branch.