Reference count underflow in shiftfs
CVE-2019-15791

7.1HIGH

Key Information:

Vendor

Ubuntu

Status
Shiftfs In The Linux Kernel
Vendor
CVE Published:
24 April 2020

What is CVE-2019-15791?

In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() installs an fd referencing a file from the lower filesystem without taking an additional reference to that file. After the btrfs ioctl completes this fd is closed, which then puts a reference to that file, leading to a refcount underflow.

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Affected Version(s)

Shiftfs in the Linux kernel 5.3.0-11.12 < 5.3 kernel*

Shiftfs in the Linux kernel 5.0 kernel < 5.0.0-35.38

References

https://usn.ubuntu.com/usn/usn-4183-1
x_refsource_MISC
https://usn.ubuntu.com/usn/usn-4184-1
x_refsource_MISC
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/l...
x_refsource_MISC

CVSS V3.1

Score:
7.1
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Jann Horn of Google Project Zero
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