CVE-2026-98996 — fs: don't silently unmount busy mounts

Affected: Linux

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

fs: don't silently unmount busy mounts

The propagate_mount_busy() helper exists to decide whether a synchronous can suceed. It does that by looking at the copies of the victims in the mounts its parent propagates to. One of those functions from propagation hell.

It skips a copy that has child mounts except for the case of a single child mount covering the copy's root. That algorithm used to be exact. It isn't anymore.

Originally only childless copies were unmounted during propagation. And 1064f874abc0 ("mnt: Tuck mounts under others instead of creating shadow/side mounts.") ended up adding covered mounts to both sides in one go.

Along came 99b19d16471e ("mnt: In propgate_umount handle visiting mounts in any order") and that started to unmount more than before:

[1]: A copy of a mount is unmounted when each of its children is either its overmount or a copy of the victim itself. In the former case the overmount gets reparented. In the latter case the copy of the victim will end up being unmounted.

So propagate_umount() ended up being rewritten without adjusting propagate_mount_busy(). And currently propagate_mount_busy() doesn't look at copies of the victim that have two or more children nor a single child that is not the overmount.

So any such copy in [1] is not checked for references. The result is that a synchronous unmount succeeds, pulling out a mount that is still in use.

A contain…

USN-9018-1 — linux, linux-aws, linux-gcp, linux-ibm, linux-oem-7.0, linux-oracle vulnerabilities

Affected: Ubuntu:26.04:LTS: linux, Ubuntu:26.04:LTS: linux-aws, Ubuntu:26.04:LTS: linux-gcp, Ubuntu:26.04:LTS: linux-ibm, Ubuntu:26.04:LTS: linux-oem-7.0, Ubuntu:26.04:LTS: linux-oracle

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - Network file systems library; - Stream parser; - ARM64 architecture; - PowerPC architecture; - RISC-V architecture; - S390 architecture; - User-Mode Linux (UML); - x86 architecture; - Block layer subsystem; - Android drivers; - Bluetooth drivers; - TPM device driver; - DPLL subsystem; - EDAC drivers; - GPIO subsystem; - GPU drivers; - HID subsystem; - IIO subsystem; - IIO ADC drivers; - InfiniBand drivers; - Input Device (Miscellaneous) drivers; - Multiple devices driver; - MemoryStick subsystem; - MMC subsystem; - MTD block device drivers; - Network drivers; - Ethernet bonding driver; - Mellanox network drivers; - STMicroelectronics network drivers; - Ethernet team driver; - MediaTek network drivers; - NVME drivers; - Device tree and open firmware driver; - Power sequencing drivers; - Voltage and Current Regulator drivers; - Real Time Clock drivers; - SCSI subsystem; - Greybus lights staging drivers; - Trusted Execution Environment drivers; - Thunderbolt and USB4 drivers; - TTY drivers; - Cadence USB3 driver; - USB Device Class drivers; - USB core drivers; - DesignWare USB2 driver; - DesignWare USB3 driver; - USB Gadget drivers; - USB Serial drivers; - USB Mass Storage drivers; - USB Type-C suppor…

Most recent entries from all

CVE-2026-98996 — fs: don't silently unmount busy mounts

USN-9018-1 — linux, linux-aws, linux-gcp, linux-ibm, linux-oem-7.0, linux-oracle vulnerabilities