CVE-2026-45984gfs2: Fix use-after-free in iomap inline data write path

Official description

In the Linux kernel, the following vulnerability has been resolved: gfs2: Fix use-after-free in iomap inline data write path The inline data buffer head (dibh) is being released prematurely in gfs2_iomap_begin() via release_metapath() while iomap->inline_data still points to dibh->b_data. This causes a use-after-free when iomap_write_end_inline() later attempts to write to the inline data area. The bug sequence: 1. gfs2_iomap_begin() calls gfs2_meta_inode_buffer() to read inode metadata into dibh 2. Sets iomap->inline_data = dibh->b_data + sizeof(struct gfs2_dinode) 3. Calls release_metapath() which calls brelse(dibh), dropping refcount to 0 4. kswapd reclaims the page (~39ms later in the syzbot report) 5. iomap_write_end_inline() tries to memcpy() to iomap->inline_data 6. KASAN detects use-after-free write to freed memory Fix by storing dibh in iomap->private and incrementing its refcount with get_bh() in gfs2_iomap_begin(). The buffer is then properly released in gfs2_iomap_end() after the inline write completes, ensuring the page stays alive for the entire iomap operation. Note: A C reproducer is not available for this issue. The fix is based on analysis of the KASAN report and code review showing the buffer head is freed before use. [agruenba: Take buffer head reference in gfs2_iomap_begin() to avoid leaks in gfs2_iomap_get() and gfs2_iomap_alloc().]

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1403989d1b502f4a2c0d0b42ccf1c25748442eff
• https://git.kernel.org/stable/c/1cae1bafdf9caa9b462b19af06b1a06902e4e142
• https://git.kernel.org/stable/c/764c3c84b5683e608f43735c803a5f415046686c
• https://git.kernel.org/stable/c/d87268326b277af3665237ac76a73dd9fa8e21b4
• https://git.kernel.org/stable/c/87d4954b5c59735a99ea98cb208d47130f6dce7d
• https://git.kernel.org/stable/c/6d76febba07c40bcf358f63216d36ea68cf1c215
• https://git.kernel.org/stable/c/815ddd27c0c7171a99fe802fdb19098ddef8b19d
• https://git.kernel.org/stable/c/faddeb848305e79db89ee0479bb0e33380656321
• https://access.redhat.com/security/cve/CVE-2026-45984 vdb-entry, x_refsource_REDHAT
• RHBZ#2481922 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45984.json x_sadp-csaf-vex
• https://access.redhat.com/errata/RHSA-2026:61692 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:63189 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:51603 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:36767 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:38902 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:27789 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59143 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:33743 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59146 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:35894 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:55444 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59142 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59147 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59145 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59148 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:59149 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:36049 vendor-advisory, x_refsource_REDHAT
• https://access.redhat.com/errata/RHSA-2026:51604 vendor-advisory, x_refsource_REDHAT