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CVE-2026-31715

f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io()

Published
Last modified
published
Not listed in CISA KEV
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io() The xfstests case "generic/107" and syzbot have both reported a NULL pointer dereference. The concurrent scenario that triggers the panic is as follows: F2FS_WB_CP_DATA write callback umount • f2fs_write_checkpoint • f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA) • blk_mq_end_request • bio_endio • f2fs_write_end_io : dec_page_count(sbi, F2FS_WB_CP_DATA) : wake_up(&sbi->cp_wait) • kill_f2fs_super • kill_block_super • f2fs_put_super : iput(sbi->node_inode) : sbi->node_inode = NULL : f2fs_in_warm_node_list • is_node_folio // sbi->node_inode is NULL and panic The root cause is that f2fs_put_super() calls iput(sbi->node_inode) and sets sbi->node_inode to NULL after sbi->nr_pages[F2FS_WB_CP_DATA] is decremented to zero. As a result, f2fs_in_warm_node_list() may dereference a NULL node_inode when checking whether a folio belongs to the node inode, leading to a panic. This patch fixes the issue by calling f2fs_in_warm_node_list() before decrementing sbi->nr_pages[F2FS_WB_CP_DATA], thus preventing the use-after-free condition.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    Version range not reported

  • Linux Linux

    4.19

References 8

git.kernel.org