CVE-2025-40054

*** Pendiente de traducción *** In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> f2fs: fix UAF issue in f2fs_merge_page_bio()<br /> <br /> As JY reported in bugzilla [1],<br /> <br /> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000<br /> pc : [0xffffffe51d249484] f2fs_is_cp_guaranteed+0x70/0x98<br /> lr : [0xffffffe51d24adbc] f2fs_merge_page_bio+0x520/0x6d4<br /> CPU: 3 UID: 0 PID: 6790 Comm: kworker/u16:3 Tainted: P B W OE 6.12.30-android16-5-maybe-dirty-4k #1 5f7701c9cbf727d1eebe77c89bbbeb3371e895e5<br /> Tainted: [P]=PROPRIETARY_MODULE, [B]=BAD_PAGE, [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE<br /> Workqueue: writeback wb_workfn (flush-254:49)<br /> Call trace:<br /> f2fs_is_cp_guaranteed+0x70/0x98<br /> f2fs_inplace_write_data+0x174/0x2f4<br /> f2fs_do_write_data_page+0x214/0x81c<br /> f2fs_write_single_data_page+0x28c/0x764<br /> f2fs_write_data_pages+0x78c/0xce4<br /> do_writepages+0xe8/0x2fc<br /> __writeback_single_inode+0x4c/0x4b4<br /> writeback_sb_inodes+0x314/0x540<br /> __writeback_inodes_wb+0xa4/0xf4<br /> wb_writeback+0x160/0x448<br /> wb_workfn+0x2f0/0x5dc<br /> process_scheduled_works+0x1c8/0x458<br /> worker_thread+0x334/0x3f0<br /> kthread+0x118/0x1ac<br /> ret_from_fork+0x10/0x20<br /> <br /> [1] https://bugzilla.kernel.org/show_bug.cgi?id=220575<br /> <br /> The panic was caused by UAF issue w/ below race condition:<br /> <br /> kworker<br /> - writepages<br /> - f2fs_write_cache_pages<br /> - f2fs_write_single_data_page<br /> - f2fs_do_write_data_page<br /> - f2fs_inplace_write_data<br /> - f2fs_merge_page_bio<br /> - add_inu_page<br /> : cache page #1 into bio &amp; cache bio in<br /> io-&gt;bio_list<br /> - f2fs_write_single_data_page<br /> - f2fs_do_write_data_page<br /> - f2fs_inplace_write_data<br /> - f2fs_merge_page_bio<br /> - add_inu_page<br /> : cache page #2 into bio which is linked<br /> in io-&gt;bio_list<br /> write<br /> - f2fs_write_begin<br /> : write page #1<br /> - f2fs_folio_wait_writeback<br /> - f2fs_submit_merged_ipu_write<br /> - f2fs_submit_write_bio<br /> : submit bio which inclues page #1 and #2<br /> <br /> software IRQ<br /> - f2fs_write_end_io<br /> - fscrypt_free_bounce_page<br /> : freed bounced page which belongs to page #2<br /> - inc_page_count( , WB_DATA_TYPE(data_folio), false)<br /> : data_folio points to fio-&gt;encrypted_page<br /> the bounced page can be freed before<br /> accessing it in f2fs_is_cp_guarantee()<br /> <br /> It can reproduce w/ below testcase:<br /> Run below script in shell #1:<br /> for ((i=1;i&gt;0;i++)) do xfs_io -f /mnt/f2fs/enc/file \<br /> -c "pwrite 0 32k" -c "fdatasync"<br /> <br /> Run below script in shell #2:<br /> for ((i=1;i&gt;0;i++)) do xfs_io -f /mnt/f2fs/enc/file \<br /> -c "pwrite 0 32k" -c "fdatasync"<br /> <br /> So, in f2fs_merge_page_bio(), let&amp;#39;s avoid using fio-&gt;encrypted_page after<br /> commit page into internal ipu cache.