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High

Use-after-free in Linux kernel GFS2 iomap inline data write path

IdentifiersCVE-2026-45984CWE-416· Use After Free

CVE-2026-45984 is a use-after-free vulnerability in the Linux kernel GFS2 filesystem inline-data write path. In gfs2_iomap_begin(), inode metadata is read into the buffer head dibh via gfs2_meta_inode_buffer(), and iomap->inline_data is then set to point into dibh->b_data at an offset past struct gfs2_dinode. However, release_metapath() is subsequently called and drops the final reference to dibh via brelse(dibh), while iomap->inline_data still references that memory. If the backing page is reclaimed before the write completes, iomap_write_end_inline() later performs a memcpy() into freed memory, resulting in a kernel use-after-free write. The upstream fix preserves the buffer head for the lifetime of the iomap operation by storing dibh in iomap->private, taking an additional reference with get_bh() in gfs2_iomap_begin(), and releasing it in gfs2_iomap_end() after the inline write completes.

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Impact, mitigation & remediation

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Impact

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Successful exploitation causes a kernel-space use-after-free write in the GFS2 write path. This can lead to kernel memory corruption, system instability, crashes, and denial of service. Because the write occurs in freed kernel memory, there is also potential for more severe consequences such as privilege escalation or other integrity impacts, although the provided content does not document a public exploit or confirmed code-execution path.

Mitigation

If you can’t patch tonight, do this now.

Until patched kernels can be deployed, reduce exposure by limiting local access to systems using the GFS2 filesystem and minimizing untrusted write activity against GFS2-mounted filesystems, particularly paths that exercise inline data writes. Where operationally feasible, avoid use of affected GFS2 configurations on untrusted multi-user systems. No specific runtime-only mitigation beyond applying the kernel fix is provided in the available content.

Remediation

Patch, then assume compromise.

Upgrade to a Linux kernel release containing the fix for CVE-2026-45984. The remediation is to retain the inline-data buffer head across the full iomap operation: store dibh in iomap->private, increment its reference count with get_bh() in gfs2_iomap_begin(), and release it in gfs2_iomap_end() only after the inline write completes. Vendor kernel updates from downstream distributors should also be applied where applicable.
PUBLIC EXPLOITS

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

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VendorProductType
LinuxLinux Kerneloperating_system
Rocky LinuxKerneloperating_system

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