hfsplus: Verify inode mode when loading from disk

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: hfsplus: Verify inode mode 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 16bits "mode" field loaded from disk are corrupted. According to [1], the permissions field was treated as reserved in Mac OS 8 and 9. According to [2], the reserved field was explicitly initialized with 0, and that field must remain 0 as long as reserved. Therefore, when the "mode" field is not 0 (i.e. no longer reserved), the file must be S_IFDIR if dir == 1, and the file must be one of S_IFREG/S_IFLNK/S_IFCHR/ S_IFBLK/S_IFIFO/S_IFSOCK if dir == 0.

References

• https://git.kernel.org/stable/c/6f768724aabd5b321c5b8f15acdca11e4781cf32
• https://git.kernel.org/stable/c/d92333c7a35856e419500e7eed72dac1afa404a5
• https://git.kernel.org/stable/c/001f44982587ad462b3002ee40c75e8df67d597d
• https://git.kernel.org/stable/c/05ec9af3cc430683c97f76027e1c55ac6fd25c59
• https://git.kernel.org/stable/c/edfb2e602b5ba5ca6bf31cbac20b366efb72b156
• https://git.kernel.org/stable/c/91f114bffa36ce56d0e1f60a0a44fc09baaefc79
• https://git.kernel.org/stable/c/005d4b0d33f6b4a23d382b7930f7a96b95b01f39