Out-of-bounds Write Affecting kernel-uek-doc package, versions <0:6.12.0-200.74.27.el9uek

Note: Versions mentioned in the description apply only to the upstream kernel-uek-doc package and not the kernel-uek-doc package as distributed by Oracle. See How to fix? for Oracle:9 relevant fixed versions and status.

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

f2fs: fix to avoid mapping wrong physical block for swapfile

Xiaolong Guo reported a f2fs bug in bugzilla [1]

[1] https://bugzilla.kernel.org/show_bug.cgi?id=220951

Quoted:

"When using stress-ng's swap stress test on F2FS filesystem with kernel 6.6+, the system experiences data corruption leading to either: 1 dm-verity corruption errors and device reboot 2 F2FS node corruption errors and boot hangs

The issue occurs specifically when: 1 Using F2FS filesystem (ext4 is unaffected) 2 Swapfile size is less than F2FS section size (2MB) 3 Swapfile has fragmented physical layout (multiple non-contiguous extents) 4 Kernel version is 6.6+ (6.1 is unaffected)

The root cause is in check_swap_activate() function in fs/f2fs/data.c. When the first extent of a small swapfile (< 2MB) is not aligned to section boundaries, the function incorrectly treats it as the last extent, failing to map subsequent extents. This results in incorrect swap_extent creation where only the first extent is mapped, causing subsequent swap writes to overwrite wrong physical locations (other files' data).

Steps to Reproduce 1 Setup a device with F2FS-formatted userdata partition 2 Compile stress-ng from https://github.com/ColinIanKing/stress-ng 3 Run swap stress test: (Android devices) adb shell "cd /data/stressng; ./stress-ng-64 --metrics-brief --timeout 60 --swap 0"

Log: 1 Ftrace shows in kernel 6.6, only first extent is mapped during second f2fs_map_blocks call in check_swap_activate(): stress-ng-swap-8990: f2fs_map_blocks: ino=11002, file offset=0, start blkaddr=0x43143, len=0x1 (Only 4KB mapped, not the full swapfile) 2 in kernel 6.1, both extents are correctly mapped: stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=0, start blkaddr=0x13cd4, len=0x1 stress-ng-swap-5966: f2fs_map_blocks: ino=28011, file offset=1, start blkaddr=0x60c84b, len=0xff

The problematic code is in check_swap_activate(): if ((pblock - SM_I(sbi)->main_blkaddr) % blks_per_sec || nr_pblocks % blks_per_sec || !f2fs_valid_pinned_area(sbi, pblock)) { bool last_extent = false;

not_aligned++;

nr_pblocks = roundup(nr_pblocks, blks_per_sec);
if (cur_lblock + nr_pblocks > sis->max)
    nr_pblocks -= blks_per_sec;
/* this extent is last one */
if (!nr_pblocks) {
    nr_pblocks = last_lblock - cur_lblock;
    last_extent = true;
}
ret = f2fs_migrate_blocks(inode, cur_lblock, nr_pblocks);
if (ret) {
    if (ret == -ENOENT)
        ret = -EINVAL;
    goto out;
}
if (!last_extent)
    goto retry;

}

When the first extent is unaligned and roundup(nr_pblocks, blks_per_sec) exceeds sis->max, we subtract blks_per_sec resulting in nr_pblocks = 0. The code then incorrectly assumes this is the last extent, sets nr_pblocks = last_lblock - cur_lblock (entire swapfile), and performs migration. After migration, it doesn't retry mapping, so subsequent extents are never processed. "

In order to fix this issue, we need to lookup block mapping info after we migrate all blocks in the tail of swapfile.

• https://linux.oracle.com/cve/CVE-2026-23233.html
• https://linux.oracle.com/errata/ELSA-2026-50160.html
• https://git.kernel.org/stable/c/1ff415eef513bf12deb058fc50d57788c46c48e6
• https://git.kernel.org/stable/c/5c145c03188bc9ba1c29e0bc4d527a5978fc47f9
• https://git.kernel.org/stable/c/607cb9d83838d2cd9f0406c2403ed61aadf0edff
• https://git.kernel.org/stable/c/d4534a7f6c92baaf7e12a45fc6e37332cafafc33
• https://git.kernel.org/stable/c/fee27b69dde1a05908b350eea42937af2387c4fe