bfs: Reconstruct file type when loading from disk

Summary

In the Linux kernel, the following vulnerability has been resolved: bfs: Reconstruct file type when loading from disk syzbot is reporting that S_IFMT bits of inode->i_mode can become bogus when the S_IFMT bits of the 32bits "mode" field loaded from disk are corrupted or when the 32bits "attributes" field loaded from disk are corrupted. A documentation says that BFS uses only lower 9 bits of the "mode" field. But I can't find an explicit explanation that the unused upper 23 bits (especially, the S_IFMT bits) are initialized with 0. Therefore, ignore the S_IFMT bits of the "mode" field loaded from disk. Also, verify that the value of the "attributes" field loaded from disk is either BFS_VREG or BFS_VDIR (because BFS supports only regular files and the root directory).

Timeline

1. Dec 16, 2025, 2:47 PM UTCCVE published
2. Oct 15, 2026, 1:09 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in d0c5ec1f57d8fbb953f166a27d9d32473dc8f3e4; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in aeccd6743ee4fdd1ab8cfcbb5b9a20b613418f6d; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 8f73336b75bd3457b6f9410f2a0601a238f32238; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in a9f626396bfe66f49b743601e862767928237cc0; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 77899444d46162aeb65f229590c26ba266864223; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in a8cb796e7e2cb7971311ba236922f5e7e1be77e6; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 34ab4c75588c07cca12884f2bf6b0347c7a13872

• Linux Linux

  2.6.12

• KernelLinux

  From 2.6.12 · fixed in 5.10.248; From 5.11.0 · fixed in 5.15.198; From 5.16.0 · fixed in 6.1.160; From 6.2.0 · fixed in 6.6.120; From 6.7.0 · fixed in 6.12.62; From 6.13.0 · fixed in 6.17.12

References 7