CVE-2021-47492

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> mm, thp: bail out early in collapse_file for writeback page<br /> <br /> Currently collapse_file does not explicitly check PG_writeback, instead,<br /> page_has_private and try_to_release_page are used to filter writeback<br /> pages. This does not work for xfs with blocksize equal to or larger<br /> than pagesize, because in such case xfs has no page-&gt;private.<br /> <br /> This makes collapse_file bail out early for writeback page. Otherwise,<br /> xfs end_page_writeback will panic as follows.<br /> <br /> page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32<br /> aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:"libtest.so"<br /> flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback)<br /> raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8<br /> raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000<br /> page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u mem_cgroup:ffff0000c3e9a000<br /> ------------[ cut here ]------------<br /> kernel BUG at include/linux/mm.h:1212!<br /> Internal error: Oops - BUG: 0 [#1] SMP<br /> Modules linked in:<br /> BUG: Bad page state in process khugepaged pfn:84ef32<br /> xfs(E)<br /> page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32<br /> libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ...<br /> CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ...<br /> pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)<br /> Call trace:<br /> end_page_writeback+0x1c0/0x214<br /> iomap_finish_page_writeback+0x13c/0x204<br /> iomap_finish_ioend+0xe8/0x19c<br /> iomap_writepage_end_bio+0x38/0x50<br /> bio_endio+0x168/0x1ec<br /> blk_update_request+0x278/0x3f0<br /> blk_mq_end_request+0x34/0x15c<br /> virtblk_request_done+0x38/0x74 [virtio_blk]<br /> blk_done_softirq+0xc4/0x110<br /> __do_softirq+0x128/0x38c<br /> __irq_exit_rcu+0x118/0x150<br /> irq_exit+0x1c/0x30<br /> __handle_domain_irq+0x8c/0xf0<br /> gic_handle_irq+0x84/0x108<br /> el1_irq+0xcc/0x180<br /> arch_cpu_idle+0x18/0x40<br /> default_idle_call+0x4c/0x1a0<br /> cpuidle_idle_call+0x168/0x1e0<br /> do_idle+0xb4/0x104<br /> cpu_startup_entry+0x30/0x9c<br /> secondary_start_kernel+0x104/0x180<br /> Code: d4210000 b0006161 910c8021 94013f4d (d4210000)<br /> ---[ end trace 4a88c6a074082f8c ]---<br /> Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt