CVE-2025-40054: f2fs: fix UAF issue in f2fs_merge_page_bio()
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix UAF issue in f2fsmergepagebio()
As JY reported in bugzilla [1],
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 pc : [0xffffffe51d249484] f2fsiscpguaranteed+0x70/0x98 lr : [0xffffffe51d24adbc] f2fsmergepagebio+0x520/0x6d4 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 Tainted: [P]=PROPRIETARYMODULE, [B]=BADPAGE, [W]=WARN, [O]=OOTMODULE, [E]=UNSIGNEDMODULE Workqueue: writeback wbworkfn (flush-254:49) Call trace: f2fsiscpguaranteed+0x70/0x98 f2fsinplacewritedata+0x174/0x2f4 f2fsdowritedatapage+0x214/0x81c f2fswritesingledatapage+0x28c/0x764 f2fswritedatapages+0x78c/0xce4 dowritepages+0xe8/0x2fc writebacksingleinode+0x4c/0x4b4 writebacksbinodes+0x314/0x540 writebackinodeswb+0xa4/0xf4 wbwriteback+0x160/0x448 wbworkfn+0x2f0/0x5dc processscheduledworks+0x1c8/0x458 workerthread+0x334/0x3f0 kthread+0x118/0x1ac retfromfork+0x10/0x20
[1] https://bugzilla.kernel.org/showbug.cgi?id=220575
The panic was caused by UAF issue w/ below race condition:
kworker - writepages - f2fswritecachepages - f2fswritesingledatapage - f2fsdowritedatapage - f2fsinplacewritedata - f2fsmergepagebio - addinupage : cache page #1 into bio & cache bio in io->biolist - f2fswritesingledatapage - f2fsdowritedatapage - f2fsinplacewritedata - f2fsmergepagebio - addinupage : cache page #2 into bio which is linked in io->biolist write - f2fswritebegin : write page #1 - f2fsfoliowaitwriteback - f2fssubmitmergedipuwrite - f2fssubmitwritebio : submit bio which inclues page #1 and #2
software IRQ - f2fswriteendio - fscryptfreebouncepage : freed bounced page which belongs to page #2 - incpagecount( , WBDATATYPE(datafolio), false) : datafolio points to fio->encryptedpage the bounced page can be freed before accessing it in f2fsiscpguarantee()
It can reproduce w/ below testcase: Run below script in shell #1: for ((i=1;i>0;i++)) do xfsio -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync"
Run below script in shell #2: for ((i=1;i>0;i++)) do xfsio -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync"
So, in f2fsmergepagebio(), let's avoid using fio->encryptedpage after commit page into internal ipu cache.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.13-1 - Upgrade
Upgrade
debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Compensating control
In f2fs_merge_page_bio(), avoid using fio->encrypted_page after committing the page into the internal IPU cache, preventing access to a freed bounced page.
Event History
Frequently Asked Questions
What is the severity of CVE-2025-40054?
CVE-2025-40054 has a medium severity rating due to the potential for a use-after-free vulnerability in the Linux kernel.
How do I fix CVE-2025-40054?
To resolve CVE-2025-40054, you should update the Linux kernel to the latest patched version that addresses this vulnerability.
What impact does CVE-2025-40054 have on my system?
CVE-2025-40054 can lead to a kernel panic or system crash, impacting system stability and security.
Which versions of the Linux kernel are affected by CVE-2025-40054?
CVE-2025-40054 affects specific versions of the Linux kernel prior to the released fixes.
Is CVE-2025-40054 being actively exploited?
As of now, there is no public information indicating that CVE-2025-40054 is actively being exploited in the wild.