In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix folio_queue ENOMEM in writeback by adding a mempool
Fix the handling of folio_queue allocation failure in writeback by adding a mempool and passing in gfp_t flags to the rolling buffer functions that allocate memory, using the mempool if gfp != GFP_KERNEL.
This is then extended upwards and the gfp to be used for a request is stored in the netfs_io_request struct and is then used for both requests and subrequests, eliminating the sleeping loops there.
The failure caused:
folio != NULL
WARNING: fs/netfs/write_issue.c:603 at netfs_writepages+0x883/0xa10 fs/netfs/write_issue.c:603, CPU#3: syz.0.17/5919