CVE-2026-53018: f2fs: avoid reading already updated pages during GC

CVE-2026-53018: f2fs: avoid reading already updated pages during GC

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

f2fs: avoid reading already updated pages during GC

We found the following issue during fuzz testing:

page: refcount:3 mapcount:0 mapping:00000000b6e89c65 index:0x18b2dc pfn:0x161ba9
memcg:f8ffff800e269c00
aops:f2fs_meta_aops ino:2
flags: 0x52880000000080a9(locked|waiters|uptodate|lru|private|zone=1|kasantag=0x4a)
raw: 52880000000080a9 fffffffec6e17588 fffffffec0ccc088 a7ffff8067063618
raw: 000000000018b2dc 0000000000000009 00000003ffffffff f8ffff800e269c00
page dumped because: VM_BUG_ON_FOLIO(folio_test_uptodate(folio))
page_owner tracks the page as allocated
 post_alloc_hook+0x58c/0x5ec
 prep_new_page+0x34/0x284
 get_page_from_freelist+0x2dcc/0x2e8c
 __alloc_pages_noprof+0x280/0x76c
 __folio_alloc_noprof+0x18/0xac
 __filemap_get_folio+0x6bc/0xdc4
 pagecache_get_page+0x3c/0x104
 do_garbage_collect+0x5c78/0x77a4
 f2fs_gc+0xd74/0x25f0
 gc_thread_func+0xb28/0x2930
 kthread+0x464/0x5d8
 ret_from_fork+0x10/0x20
------------[ cut here ]------------
kernel BUG at mm/filemap.c:1563!
 folio_end_read+0x140/0x168
 f2fs_finish_read_bio+0x5c4/0xb80
 f2fs_read_end_io+0x64c/0x708
 bio_endio+0x85c/0x8c0
 blk_update_request+0x690/0x127c
 scsi_end_request+0x9c/0xb8c
 scsi_io_completion+0xf0/0x250
 scsi_finish_command+0x430/0x45c
 scsi_complete+0x178/0x6d4
 blk_mq_complete_request+0xcc/0x104
 scsi_done_internal+0x214/0x454
 scsi_done+0x24/0x34

which is similar to the problem reported by syzbot:
https://syzkaller.appspot.com/bug?extid=3686758660f980b402dc

This case is consistent with the description in commit 9bf1a3f
("f2fs: avoid GC causing encrypted file corrupted"):
Page 1 is moved from blkaddr A to blkaddr B by move_data_block, and after
being written it is marked as uptodate. Then, Page 1 is moved from blkaddr
B to blkaddr C, VM_BUG_ON_FOLIO was triggered in the endio initiated by
ra_data_block.

There is no need to read Page 1 again from blkaddr B, since it has already
been updated. Therefore, avoid initiating I/O in this case.

The Linux kernel CVE team has assigned CVE-2026-53018 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.19 with commit 6aa58d8ad20a3323f42274c25820a6f54192422d and fixed in 6.18.33 with commit 4623c251496b99c530ce225c05334f4eac8b933a
	Issue introduced in 4.19 with commit 6aa58d8ad20a3323f42274c25820a6f54192422d and fixed in 7.0.10 with commit b663ebb8a340eae5442e605b6acd2cff5677f016
	Issue introduced in 4.19 with commit 6aa58d8ad20a3323f42274c25820a6f54192422d and fixed in 7.1 with commit 570e2ccc7cb35fe720106964e65060602d3d2ac4

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-53018
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/f2fs/gc.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4623c251496b99c530ce225c05334f4eac8b933a
	https://git.kernel.org/stable/c/b663ebb8a340eae5442e605b6acd2cff5677f016
	https://git.kernel.org/stable/c/570e2ccc7cb35fe720106964e65060602d3d2ac4