=====================================================
BUG: KMSAN: uninit-value in vring_map_one_sg drivers/virtio/virtio_ring.c:339 [inline]
BUG: KMSAN: uninit-value in virtqueue_add_split drivers/virtio/virtio_ring.c:544 [inline]
BUG: KMSAN: uninit-value in virtqueue_add+0x1d8a/0x6220 drivers/virtio/virtio_ring.c:1795
 vring_map_one_sg drivers/virtio/virtio_ring.c:339 [inline]
 virtqueue_add_split drivers/virtio/virtio_ring.c:544 [inline]
 virtqueue_add+0x1d8a/0x6220 drivers/virtio/virtio_ring.c:1795
 virtqueue_add_sgs+0x182/0x1a0 drivers/virtio/virtio_ring.c:1829
 __virtscsi_add_cmd drivers/scsi/virtio_scsi.c:459 [inline]
 virtscsi_add_cmd+0x861/0xb00 drivers/scsi/virtio_scsi.c:493
 virtscsi_queuecommand+0x95d/0xb10 drivers/scsi/virtio_scsi.c:590
 scsi_dispatch_cmd+0x54e/0xbf0 drivers/scsi/scsi_lib.c:1517
 scsi_queue_rq+0x415c/0x4820 drivers/scsi/scsi_lib.c:1745
 blk_mq_dispatch_rq_list+0x1481/0x40e0 block/blk-mq.c:1896
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:173 [inline]
 blk_mq_do_dispatch_sched+0xdd1/0x16d0 block/blk-mq-sched.c:187
 __blk_mq_sched_dispatch_requests+0x442/0x630
 blk_mq_sched_dispatch_requests+0x159/0x2c0 block/blk-mq-sched.c:339
 __blk_mq_run_hw_queue+0xee/0x260 block/blk-mq.c:2013
 __blk_mq_delay_run_hw_queue+0x191/0x7c0 block/blk-mq.c:2090
 blk_mq_run_hw_queue+0x4d7/0x7d0 block/blk-mq.c:2141
 blk_mq_sched_insert_requests+0x4e5/0x760 block/blk-mq-sched.c:493
 blk_mq_dispatch_plug_list+0x66b/0x880 block/blk-mq.c:2621
 blk_mq_flush_plug_list+0x759/0x8e0 block/blk-mq.c:2663
 __blk_flush_plug+0x5f6/0x680 block/blk-core.c:1206
 blk_finish_plug+0x71/0x90 block/blk-core.c:1230
 wb_writeback+0xdc3/0xe30 fs/fs-writeback.c:2073
 wb_do_writeback+0x25a/0x11c0 fs/fs-writeback.c:2182
 wb_workfn+0x194/0x600 fs/fs-writeback.c:2222
 process_one_work+0xb27/0x13e0 kernel/workqueue.c:2289
 worker_thread+0x1076/0x1d60 kernel/workqueue.c:2436
 kthread+0x31b/0x430 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

Uninit was created at:
 __alloc_pages+0x9f1/0xe80 mm/page_alloc.c:5466
 alloc_pages+0x927/0xc00 mm/mempolicy.c:2272
 folio_alloc+0x3e/0x120 mm/mempolicy.c:2282
 filemap_alloc_folio mm/filemap.c:996 [inline]
 __filemap_get_folio+0xe5b/0x1b30 mm/filemap.c:1992
 pagecache_get_page+0x4a/0x4d0 mm/folio-compat.c:126
 grab_cache_page_write_begin+0x51/0x70 mm/folio-compat.c:138
 ext4_write_begin+0x3a4/0x3060 fs/ext4/inode.c:1186
 ext4_da_write_begin+0x609/0x1190 fs/ext4/inode.c:2961
 generic_perform_write+0x3f1/0xbf0 mm/filemap.c:3779
 ext4_buffered_write_iter+0x57b/0x960 fs/ext4/file.c:270
 ext4_file_write_iter+0x13a6/0x3450
 call_write_iter include/linux/fs.h:2058 [inline]
 new_sync_write fs/read_write.c:504 [inline]
 vfs_write+0xcf0/0x1810 fs/read_write.c:591
 ksys_write+0x21b/0x4e0 fs/read_write.c:644
 __do_sys_write fs/read_write.c:656 [inline]
 __se_sys_write fs/read_write.c:653 [inline]
 __ia32_sys_write+0x8d/0xd0 fs/read_write.c:653
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0x95/0xf0 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203
 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:246
 entry_SYSENTER_compat_after_hwframe+0x53/0x62

Bytes 4-4095 of 4096 are uninitialized
Memory access of size 4096 starts at ffff88801b7c5000

CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.19.0-rc4-syzkaller-31333-g97117d69c353 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Workqueue: writeback wb_workfn (flush-8:0)
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