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7.1 High

CVE-2019-15794 Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3…

Description

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vm_file points. On upstream kernels this is not an issue, as no callers dereference vm_file following after call_mmap() returns an error. However, the aufs patchs change mmap_region() to replace the fput() using a local variable with vma_fput(), which will fput() vm_file, leading to a refcount underflow.

Affected products and versions

Product Affected versions Fixed in
Linux kernel 5.3 earliest → < 5.3.0-24.26 5.3.0-24.26
Linux kernel 5.0 earliest → < 5.0.0-37.40 5.0.0-37.40

References

Timeline

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Other CVEs of Linux kernel

The 3 CVEs of Linux kernel →
CVE-2021-3492 Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults… 8.8 High CVE-2021-3493 Linux Kernel Privilege Escalation Vulnerability 8.8 High
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