The sysrq_sysctl_handler function in kernel/sysctl.c in the Linux kernel before 2.6.39 does not require the CAP_SYS_ADMIN capability to modify the dmesg_restrict value, which allows local users to bypass intended access restrictions and read the kernel ring buffer by leveraging root privileges, as demonstrated by a root user in a Linux Containers (aka LXC) environment.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Linux_kernel | Linux | * | 2.6.39 (excluding) |
| Red Hat Enterprise Linux 6 | RedHat | kernel-0:2.6.32-220.13.1.el6 | * |
| Linux | Ubuntu | upstream | * |
| Linux-armadaxp | Ubuntu | upstream | * |
| Linux-ec2 | Ubuntu | maverick | * |
| Linux-ec2 | Ubuntu | upstream | * |
| Linux-fsl-imx51 | Ubuntu | upstream | * |
| Linux-lts-backport-maverick | Ubuntu | upstream | * |
| Linux-lts-backport-natty | Ubuntu | upstream | * |
| Linux-lts-backport-oneiric | Ubuntu | upstream | * |
| Linux-mvl-dove | Ubuntu | lucid | * |
| Linux-mvl-dove | Ubuntu | upstream | * |
| Linux-ti-omap4 | Ubuntu | upstream | * |
References
- http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=bfdc0b497faa82a0ba2f9dddcf109231dd519fcc
- http://www.openwall.com/lists/oss-security/2011/10/26/10
- https://github.com/torvalds/linux/commit/bfdc0b497faa82a0ba2f9dddcf109231dd519fcc
- http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=bfdc0b497faa82a0ba2f9dddcf109231dd519fcc
- http://www.openwall.com/lists/oss-security/2011/10/26/10
- https://github.com/torvalds/linux/commit/bfdc0b497faa82a0ba2f9dddcf109231dd519fcc