(RHSA-2017:1491) Important: kernel security and bug fix update

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

Security Fix(es):

• A flaw was found in the way memory was being allocated on the stack for user space binaries. If heap (or different memory region) and stack memory regions were adjacent to each other, an attacker could use this flaw to jump over the stack guard gap, cause controlled memory corruption on process stack or the adjacent memory region, and thus increase their privileges on the system. This is a kernel-side mitigation which increases the stack guard gap size from one page to 1 MiB to make successful exploitation of this issue more difficult. (CVE-2017-1000364, Important)

Red Hat would like to thank Qualys Research Labs for reporting this issue.

Bug Fix(es):

• Previously, a kernel panic occurred when the mcelog daemon executed a huge page memory offline. This update fixes the HugeTLB feature of the Linux kernel to check for the Page Table Entry (PTE) NULL pointer in the page_check_address() function. As a result, the kernel panic no longer occurs under the described circumstances. (BZ#1444342)

• Previously, the kdump mechanism was trying to get the lock by the vmalloc_sync_all() function during a kernel panic. Consequently, a deadlock occurred, and the crashkernel did not boot. This update fixes the vmalloc_sync_all() function to avoid synchronizing the vmalloc area on the crashing CPU. As a result, the crashkernel parameter now boots as expected, and the kernel dump is collected successfully under the described circumstances. (BZ#1443494)