Description

In the Linux kernel, the following vulnerability has been resolved: fat: avoid parent link count underflow in rmdir Corrupted FAT images can leave a directory inode with an incorrect i_nlink (e.g. 2 even though subdirectories exist). rmdir then unconditionally calls drop_nlink(dir) and can drive i_nlink to 0, triggering the WARN_ON in drop_nlink(). Add a sanity check in vfat_rmdir() and msdos_rmdir(): only drop the parent link count when it is at least 3, otherwise report a filesystem error.

References 8

• git.kernel.org https://git.kernel.org/stable/c/17866f8a0822d414cb02e621cf003a7d04396ef8
• git.kernel.org https://git.kernel.org/stable/c/7fe0de287e931e07cb96ecf1f449b2ebdb0e1115
• git.kernel.org https://git.kernel.org/stable/c/8cafcb881364af5ef3a8b9fed4db254054033d8a
• git.kernel.org https://git.kernel.org/stable/c/955c5d670b5ae07c78f4345e23a895638db96ce1
• git.kernel.org https://git.kernel.org/stable/c/9894c79fd9466612d0514be157b5c30cd93aa645
• git.kernel.org https://git.kernel.org/stable/c/cd569b87378b9c33ae13c23d6bb9d205d66f7c4b
• git.kernel.org https://git.kernel.org/stable/c/d0bb592fa9def2bace90ac8926c0a1d6fa8c1aa0
• git.kernel.org https://git.kernel.org/stable/c/d3b7ffa90f613938128432c7b2f35b7aa4bdd86b

Remediation