CVE-2023-54151: 
Linux Debian vulnerability analysis and mitigation

In the Linux kernel, the following vulnerability has been resolved:

f2fs: Fix system crash due to lack of free space in LFS

When f2fs tries to checkpoint during foreground gc in LFS mode, system crash occurs due to lack of free space if the amount of dirty node and dentry pages generated by data migration exceeds free space. The reproduction sequence is as follows.

• 20GiB capacity block device (null_blk)
• format and mount with LFS mode
• create a file and write 20,000MiB
• 4k random write on full range of the file

RIP: 0010:new_curseg+0x48a/0x510 [f2fs] Code: 55 e7 f5 89 c0 48 0f af c3 48 8b 5d c0 48 c1 e8 20 83 c0 01 89 43 6c 48 83 c4 28 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc <0f> 0b f0 41 80 4f 48 04 45 85 f6 0f 84 ba fd ff ff e9 ef fe ff ff RSP: 0018:ffff977bc397b218 EFLAGS: 00010246 RAX: 00000000000027b9 RBX: 0000000000000000 RCX: 00000000000027c0 RDX: 0000000000000000 RSI: 00000000000027b9 RDI: ffff8c25ab4e74f8 RBP: ffff977bc397b268 R08: 00000000000027b9 R09: ffff8c29e4a34b40 R10: 0000000000000001 R11: ffff977bc397b0d8 R12: 0000000000000000 R13: ffff8c25b4dd81a0 R14: 0000000000000000 R15: ffff8c2f667f9000 FS: 0000000000000000(0000) GS:ffff8c344ec80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000c00055d000 CR3: 0000000e30810003 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: allocate_segment_by_default+0x9c/0x110 [f2fs] f2fs_allocate_data_block+0x243/0xa30 [f2fs] ? __mod_lruvec_page_state+0xa0/0x150 do_write_page+0x80/0x160 [f2fs] f2fs_do_write_node_page+0x32/0x50 [f2fs] __write_node_page+0x339/0x730 [f2fs] f2fs_sync_node_pages+0x5a6/0x780 [f2fs] block_operations+0x257/0x340 [f2fs] f2fs_write_checkpoint+0x102/0x1050 [f2fs] f2fs_gc+0x27c/0x630 [f2fs] ? folio_mark_dirty+0x36/0x70 f2fs_balance_fs+0x16f/0x180 [f2fs]

This patch adds checking whether free sections are enough before checkpoint during gc.

[Jaegeuk Kim: code clean-up]