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CVE-2024-47740

Disclosure Date: October 21, 2024 •
CVE-2024-47740
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

In the Linux kernel, the following vulnerability has been resolved:

f2fs: Require FMODE_WRITE for atomic write ioctls

The F2FS ioctls for starting and committing atomic writes check for
inode_owner_or_capable(), but this does not give LSMs like SELinux or
Landlock an opportunity to deny the write access – if the caller’s FSUID
matches the inode’s UID, inode_owner_or_capable() immediately returns true.

There are scenarios where LSMs want to deny a process the ability to write
particular files, even files that the FSUID of the process owns; but this
can currently partially be bypassed using atomic write ioctls in two ways:

  • F2FS_IOC_START_ATOMIC_REPLACE + F2FS_IOC_COMMIT_ATOMIC_WRITE can
    truncate an inode to size 0
  • F2FS_IOC_START_ATOMIC_WRITE + F2FS_IOC_ABORT_ATOMIC_WRITE can revert
    changes another process concurrently made to a file

Fix it by requiring FMODE_WRITE for these operations, just like for
F2FS_IOC_MOVE_RANGE. Since any legitimate caller should only be using these
ioctls when intending to write into the file, that seems unlikely to break
anything.

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CVSS V3 Severity and Metrics
Base Score:
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Impact Score:
Unknown
Exploitability Score:
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Vector:
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Attack Vector (AV):
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Attack Complexity (AC):
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Privileges Required (PR):
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User Interaction (UI):
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Scope (S):
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Integrity (I):
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Availability (A):
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General Information

Offensive Application
Unknown
Utility Class
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Ports
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OS
Unknown
Vulnerable Versions
Linux 700f3a7c7fa5
Linux not down converted
Prerequisites
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Discovered By
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PoC Author
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Metasploit Module
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Reporter
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Vendors

  • Linux

Products

  • Linux
Technical Analysis