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CVE-2014-1737

Published: 11 May 2014

The raw_cmd_copyin function in drivers/block/floppy.c in the Linux kernel through 3.14.3 does not properly handle error conditions during processing of an FDRAWCMD ioctl call, which allows local users to trigger kfree operations and gain privileges by leveraging write access to a /dev/fd device. First, raw_cmd_ioctl calls raw_cmd_copyin. This function kmallocs space for a floppy_raw_cmd structure and stores the resulting allocation in the "rcmd" pointer argument. It then attempts to copy_from_user the structure from userspace. If this fails, an early EFAULT return is taken. The problem is that even if the early return is taken, the pointer to the non-/partially-initialized floppy_raw_cmd structure has already been returned via the "rcmd" pointer. Back out in raw_cmd_ioctl, it attempts to raw_cmd_free this pointer. raw_cmd_free attempts to free any DMA pages allocated for the raw command, kfrees the raw command structure itself, and follows the linked list, if any, of further raw commands (a user can specify the FD_RAW_MORE flag to signal that there are more raw commands to follow in a single FDRAWCMD ioctl). So, a malicious user can send a FDRAWCMD ioctl with a raw command argument structure that has some bytes inaccessible (ie. off the end of an allocated page). The copy_from_user will fail but raw_cmd_free will attempt to process the floppy_raw_cmd as if it had been fully initialized by the rest of raw_cmd_copyin. The user can control the arguments passed to fd_dma_mem_free and kfree (by making use of the linked-list feature and specifying the target address as a next-in-list structure).

From the Ubuntu security team

Matthew Daley reported a flaw in the handling of ioctl commands by the floppy disk driver in the Linux kernel. An unprivileged local user could exploit this flaw to gain administrative privileges if the floppy disk module is loaded.

Notes

AuthorNote
jdstrand
android kernels (goldfish, grouper, maguro, mako and manta) are not
supported on the Ubuntu Touch 13.10 preview kernels
android kernels (flo, goldfish, grouper, maguro, mako and manta) are
not supported on the Ubuntu Touch 14.04 preview kernels
Priority

High

Status

Package Release Status
linux
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
Patches:
Introduced by

1da177e4c3f41524e886b7f1b8a0c1fc7321cac2

Fixed by ef87dbe7614341c2e7bfe8d32fcb7028cc97442c
linux-armadaxp
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
This package is not directly supported by the Ubuntu Security Team
linux-aws
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-ec2
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-flo
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-fsl-imx51
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-gke
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-goldfish
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-grouper
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-hwe
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-hwe-edge
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-linaro-omap
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-linaro-shared
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-linaro-vexpress
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-quantal
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-raring
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-saucy
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-trusty
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-utopic
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-vivid
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-wily
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-lts-xenial
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-maguro
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-mako
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-manta
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-mvl-dove
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-qcm-msm
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-raspi2
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-snapdragon
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)
linux-ti-omap4
Launchpad, Ubuntu, Debian
upstream
Released (3.15~rc5)