f2fs: fix to avoid use-after-free for cached IPU bio

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid use-after-free for cached IPU bio xfstest generic/019 reports a bug: kernel BUG at mm/filemap.c:1619! RIP: 0010:folio_end_writeback+0x8a/0x90 Call Trace: end_page_writeback+0x1c/0x60 f2fs_write_end_io+0x199/0x420 bio_endio+0x104/0x180 submit_bio_noacct+0xa5/0x510 submit_bio+0x48/0x80 f2fs_submit_write_bio+0x35/0x300 f2fs_submit_merged_ipu_write+0x2a0/0x2b0 f2fs_write_single_data_page+0x838/0x8b0 f2fs_write_cache_pages+0x379/0xa30 f2fs_write_data_pages+0x30c/0x340 do_writepages+0xd8/0x1b0 __writeback_single_inode+0x44/0x370 writeback_sb_inodes+0x233/0x4d0 __writeback_inodes_wb+0x56/0xf0 wb_writeback+0x1dd/0x2d0 wb_workfn+0x367/0x4a0 process_one_work+0x21d/0x430 worker_thread+0x4e/0x3c0 kthread+0x103/0x130 ret_from_fork+0x2c/0x50 The root cause is: after cp_error is set, f2fs_submit_merged_ipu_write() in f2fs_write_single_data_page() tries to flush IPU bio in cache, however f2fs_submit_merged_ipu_write() missed to check validity of @bio parameter, result in submitting random cached bio which belong to other IO context, then it will cause use-after-free issue, fix it by adding additional validity check.

References

• https://git.kernel.org/stable/c/b2f423fda64fb49213aa0ed5056079cf295a5df2
• https://git.kernel.org/stable/c/9a7f63283af6befc0f91d549f4f6917dff7479a9
• https://git.kernel.org/stable/c/7d058f0ab161437369ad6e45a4b67c2886e71373
• https://git.kernel.org/stable/c/97ec6f1788cc6bee3f8c89cb908e1a2a1cd859bb
• https://git.kernel.org/stable/c/af4ce124d7bd74cb839bbdaccffbb416771a56b5
• https://git.kernel.org/stable/c/5cdb422c839134273866208dad5360835ddb9794