CVE-2023-53420

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

ntfs: Fix panic about slab-out-of-bounds caused by ntfs_listxattr()

Here is a BUG report from syzbot:

BUG: KASAN: slab-out-of-bounds in ntfs_list_ea fs/ntfs3/xattr.c:191 [inline] BUG: KASAN: slab-out-of-bounds in ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710 Read of size 1 at addr ffff888021acaf3d by task syz-executor128/3632

Call Trace: ntfs_list_ea fs/ntfs3/xattr.c:191 [inline] ntfs_listxattr+0x401/0x570 fs/ntfs3/xattr.c:710 vfs_listxattr fs/xattr.c:457 [inline] listxattr+0x293/0x2d0 fs/xattr.c:804

Fix the logic of ea_all iteration. When the ea->name_len is 0, return immediately, or Add2Ptr() would visit invalid memory in the next loop.

[almaz.alexandrovich@paragon-software.com: lines of the patch have changed]

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/3c675ddffb17a8b1e32efad5c983254af18b12c2
• https://git.kernel.org/stable/c/721b75ea2dfce53a8890dff92ae01afca8e74f88
• https://git.kernel.org/stable/c/c86a2517df6c9304db8fb12b77136ec7a5d85994
• https://git.kernel.org/stable/c/f3380d895e28a32632eb3609f5bd515adee4e5a1