Xen 3.1.1 does not prevent modification of the CR4 TSC from applications, which allows pv guests to cause a denial of service (crash).

From Red Hat Security Advisory 2008:0957 :

Updated kernel packages that resolve several security issues and fix various bugs are now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red Hat Security Response Team.

[Updated 12th November 2008] The original packages distributed with this errata had a bug which prevented the Xen kernel booting on older hardware. We have updated the packages to correct this bug.

The kernel packages contain the Linux kernel, the core of any Linux operating system.

* the Xen implementation did not prevent applications running in a para-virtualized guest from modifying CR4 TSC. This could cause a local denial of service. (CVE-2007-5907, Important)

* Tavis Ormandy reported missing boundary checks in the Virtual Dynamic Shared Objects (vDSO) implementation. This could allow a local unprivileged user to cause a denial of service or escalate privileges.
(CVE-2008-3527, Important)

* the do_truncate() and generic_file_splice_write() functions did not clear the setuid and setgid bits. This could allow a local unprivileged user to obtain access to privileged information.
(CVE-2008-4210, CVE-2008-3833, Important)

* a flaw was found in the Linux kernel splice implementation. This could cause a local denial of service when there is a certain failure in the add_to_page_cache_lru() function. (CVE-2008-4302, Important)

* a flaw was found in the Linux kernel when running on AMD64 systems.
During a context switch, EFLAGS were being neither saved nor restored.
This could allow a local unprivileged user to cause a denial of service. (CVE-2006-5755, Low)

* a flaw was found in the Linux kernel virtual memory implementation.
This could allow a local unprivileged user to cause a denial of service. (CVE-2008-2372, Low)

* an integer overflow was discovered in the Linux kernel Datagram Congestion Control Protocol (DCCP) implementation. This could allow a remote attacker to cause a denial of service. By default, remote DCCP is blocked by SELinux. (CVE-2008-3276, Low)

In addition, these updated packages fix the following bugs :

* random32() seeding has been improved.

* in a multi-core environment, a race between the QP async event-handler and the destro_qp() function could occur. This led to unpredictable results during invalid memory access, which could lead to a kernel crash.

* a format string was omitted in the call to the request_module() function.

* a stack overflow caused by an infinite recursion bug in the binfmt_misc kernel module was corrected.

* the ata_scsi_rbuf_get() and ata_scsi_rbuf_put() functions now check for scatterlist usage before calling kmap_atomic().

* a sentinel NUL byte was added to the device_write() function to ensure that lspace.name is NUL-terminated.

* in the character device driver, a range_is_allowed() check was added to the read_mem() and write_mem() functions. It was possible for an illegitimate application to bypass these checks, and access /dev/mem beyond the 1M limit by calling mmap_mem() instead. Also, the parameters of range_is_allowed() were changed to cleanly handle greater than 32-bits of physical address on 32-bit architectures.

* some of the newer Nehalem-based systems declare their CPU DSDT entries as type 'Alias'. During boot, this caused an 'Error attaching device data' message to be logged.

* the evtchn event channel device lacked locks and memory barriers.
This has led to xenstore becoming unresponsive on the Itanium(r) architecture.

* sending of gratuitous ARP packets in the Xen frontend network driver is now delayed until the backend signals that its carrier status has been processed by the stack.

* on forcedeth devices, whenever setting ethtool parameters for link speed, the device could stop receiving interrupts.

* the CIFS 'forcedirectio' option did not allow text to be appended to files.

* the gettimeofday() function returned a backwards time on Intel(r) 64.

* residual-count corrections during UNDERRUN handling were added to the qla2xxx driver.

* the fix for a small quirk was removed for certain Adaptec controllers for which it caused problems.

* the 'xm trigger init' command caused a domain panic if a userland application was running on a guest on the Intel(r) 64 architecture.

Users of kernel should upgrade to these updated packages, which contain backported patches to correct these issues.

- the Xen implementation did not prevent applications     running in a para-virtualized guest from modifying CR4     TSC. This could cause a local denial of service.
    (CVE-2007-5907, Important)

  - Tavis Ormandy reported missing boundary checks in the     Virtual Dynamic Shared Objects (vDSO) implementation.
    This could allow a local unprivileged user to cause a     denial of service or escalate privileges.
    (CVE-2008-3527, Important)

  - the do_truncate() and generic_file_splice_write()     functions did not clear the setuid and setgid bits. This     could allow a local unprivileged user to obtain access     to privileged information. (CVE-2008-4210,     CVE-2008-3833, Important)

  - a flaw was found in the Linux kernel splice     implementation. This could cause a local denial of     service when there is a certain failure in the     add_to_page_cache_lru() function. (CVE-2008-4302,     Important)

  - a flaw was found in the Linux kernel when running on     AMD64 systems. During a context switch, EFLAGS were     being neither saved nor restored. This could allow a     local unprivileged user to cause a denial of service.
    (CVE-2006-5755, Low)

  - a flaw was found in the Linux kernel virtual memory     implementation. This could allow a local unprivileged     user to cause a denial of service. (CVE-2008-2372, Low)

  - an integer overflow was discovered in the Linux kernel     Datagram Congestion Control Protocol (DCCP)     implementation. This could allow a remote attacker to     cause a denial of service. By default, remote DCCP is     blocked by SELinux. (CVE-2008-3276, Low)

In addition, these updated packages fix the following bugs :

  - random32() seeding has been improved.

  - in a multi-core environment, a race between the QP async     event-handler and the destro_qp() function could occur.
    This led to unpredictable results during invalid memory     access, which could lead to a kernel crash.

  - a format string was omitted in the call to the     request_module() function.

  - a stack overflow caused by an infinite recursion bug in     the binfmt_misc kernel module was corrected.

  - the ata_scsi_rbuf_get() and ata_scsi_rbuf_put()     functions now check for scatterlist usage before calling     kmap_atomic().

  - a sentinel NUL byte was added to the device_write()     function to ensure that lspace.name is NUL-terminated.

  - in the character device driver, a range_is_allowed()     check was added to the read_mem() and write_mem()     functions. It was possible for an illegitimate     application to bypass these checks, and access /dev/mem     beyond the 1M limit by calling mmap_mem() instead. Also,     the parameters of range_is_allowed() were changed to     cleanly handle greater than 32-bits of physical address     on 32-bit architectures.

  - some of the newer Nehalem-based systems declare their     CPU DSDT entries as type 'Alias'. During boot, this     caused an 'Error attaching device data' message to be     logged.

  - the evtchn event channel device lacked locks and memory     barriers. This has led to xenstore becoming unresponsive     on the Itanium&reg; architecture.

  - sending of gratuitous ARP packets in the Xen frontend     network driver is now delayed until the backend signals     that its carrier status has been processed by the stack.

  - on forcedeth devices, whenever setting ethtool     parameters for link speed, the device could stop     receiving interrupts.

  - the CIFS 'forcedirectio' option did not allow text to be     appended to files.

  - the gettimeofday() function returned a backwards time on     Intel&reg; 64.

  - residual-count corrections during UNDERRUN handling were     added to the qla2xxx driver.

  - the fix for a small quirk was removed for certain     Adaptec controllers for which it caused problems.

  - the 'xm trigger init' command caused a domain panic if a     userland application was running on a guest on the     Intel&reg; 64 architecture.

Updated kernel packages that resolve several security issues and fix various bugs are now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red Hat Security Response Team.

[Updated 12th November 2008] The original packages distributed with this errata had a bug which prevented the Xen kernel booting on older hardware. We have updated the packages to correct this bug.

The kernel packages contain the Linux kernel, the core of any Linux operating system.

* the Xen implementation did not prevent applications running in a para-virtualized guest from modifying CR4 TSC. This could cause a local denial of service. (CVE-2007-5907, Important)

* Tavis Ormandy reported missing boundary checks in the Virtual Dynamic Shared Objects (vDSO) implementation. This could allow a local unprivileged user to cause a denial of service or escalate privileges.
(CVE-2008-3527, Important)

* the do_truncate() and generic_file_splice_write() functions did not clear the setuid and setgid bits. This could allow a local unprivileged user to obtain access to privileged information.
(CVE-2008-4210, CVE-2008-3833, Important)

* a flaw was found in the Linux kernel splice implementation. This could cause a local denial of service when there is a certain failure in the add_to_page_cache_lru() function. (CVE-2008-4302, Important)

* a flaw was found in the Linux kernel when running on AMD64 systems.
During a context switch, EFLAGS were being neither saved nor restored.
This could allow a local unprivileged user to cause a denial of service. (CVE-2006-5755, Low)

* a flaw was found in the Linux kernel virtual memory implementation.
This could allow a local unprivileged user to cause a denial of service. (CVE-2008-2372, Low)

* an integer overflow was discovered in the Linux kernel Datagram Congestion Control Protocol (DCCP) implementation. This could allow a remote attacker to cause a denial of service. By default, remote DCCP is blocked by SELinux. (CVE-2008-3276, Low)

In addition, these updated packages fix the following bugs :

* random32() seeding has been improved.

* in a multi-core environment, a race between the QP async event-handler and the destro_qp() function could occur. This led to unpredictable results during invalid memory access, which could lead to a kernel crash.

* a format string was omitted in the call to the request_module() function.

* a stack overflow caused by an infinite recursion bug in the binfmt_misc kernel module was corrected.

* the ata_scsi_rbuf_get() and ata_scsi_rbuf_put() functions now check for scatterlist usage before calling kmap_atomic().

* a sentinel NUL byte was added to the device_write() function to ensure that lspace.name is NUL-terminated.

* in the character device driver, a range_is_allowed() check was added to the read_mem() and write_mem() functions. It was possible for an illegitimate application to bypass these checks, and access /dev/mem beyond the 1M limit by calling mmap_mem() instead. Also, the parameters of range_is_allowed() were changed to cleanly handle greater than 32-bits of physical address on 32-bit architectures.

* some of the newer Nehalem-based systems declare their CPU DSDT entries as type 'Alias'. During boot, this caused an 'Error attaching device data' message to be logged.

* the evtchn event channel device lacked locks and memory barriers.
This has led to xenstore becoming unresponsive on the Itanium(r) architecture.

* sending of gratuitous ARP packets in the Xen frontend network driver is now delayed until the backend signals that its carrier status has been processed by the stack.

* on forcedeth devices, whenever setting ethtool parameters for link speed, the device could stop receiving interrupts.

* the CIFS 'forcedirectio' option did not allow text to be appended to files.

* the gettimeofday() function returned a backwards time on Intel(r) 64.

* residual-count corrections during UNDERRUN handling were added to the qla2xxx driver.

* the fix for a small quirk was removed for certain Adaptec controllers for which it caused problems.

* the 'xm trigger init' command caused a domain panic if a userland application was running on a guest on the Intel(r) 64 architecture.

Users of kernel should upgrade to these updated packages, which contain backported patches to correct these issues.

This update fixes Xen security issues.

Two security problems were fixed: CVE-2007-5906: Xen allowed virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.

CVE-2007-5907: Xen 3.1.1 does not prevent modification of the CR4 TSC from applications, which allows pv guests to cause a denial of service (crash).

This update fixes various Xen issues.

Two security problems were fixed: CVE-2007-5906: Xen allowed virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.

CVE-2007-5907: Xen 3.1.1 does not prevent modification of the CR4 TSC from applications, which allows pv guests to cause a denial of service (crash).

Also the following bugs were fixed: 279062: Timer ISR/1: Time went backwards 340379: Xen-3.04_13138-0.52 not working with FV File-Backed VMs

This update fixes various Xen issues.

Two security problems were fixed: CVE-2007-5906: Xen allowed virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.

CVE-2007-5907: Xen 3.1.1 does not prevent modification of the CR4 TSC from applications, which allows pv guests to cause a denial of service (crash).

Also the following bugs were fixed: 279062: Timer ISR/1: Time went backwards 286859: Fix booting from SAN 310279: Kernel Panic while booting Xen 338486: xen fails to start when option 'irq= [ <value> ]' is given in domU config

This update fixes various Xen issues.

Two security problems were fixed: CVE-2007-5906: Xen allowed virtual guest system users to cause a denial of service (hypervisor crash) by using a debug register (DR7) to set certain breakpoints.

  - Xen 3.1.1 does not prevent modification of the CR4 TSC     from applications, which allows pv guests to cause a     denial of service (crash). (CVE-2007-5907)

Also the following bugs were fixed: 279062: Timer ISR/1: Time went backwards 340379: Xen-3.04_13138-0.52 not working with FV File-Backed VMs

The remote CentOS system is missing a security update which has been documented in Red Hat advisory RHSA-2008-0957.

ID	Name	Product	Family	Severity
67758	Oracle Linux 5 : kernel (ELSA-2008-0957)	Nessus	Oracle Linux Local Security Checks	high
60488	Scientific Linux Security Update : kernel on SL5.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	high
43713	CentOS 5 : kernel (CESA-2008:0957)	Nessus	CentOS Local Security Checks	high
34690	RHEL 5 : kernel (RHSA-2008:0957)	Nessus	Red Hat Local Security Checks	high
29963	openSUSE 10 Security Update : xen (xen-4901)	Nessus	SuSE Local Security Checks	medium
29891	openSUSE 10 Security Update : xen (xen-4764)	Nessus	SuSE Local Security Checks	medium
29792	openSUSE 10 Security Update : xen (xen-4854)	Nessus	SuSE Local Security Checks	medium
29791	SuSE 10 Security Update : xen (ZYPP Patch Number 4766)	Nessus	SuSE Local Security Checks	medium
801458	CentOS RHSA-2008-0957 Security Check	Log Correlation Engine	Generic	high

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CVE-2007-5907

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