Critical CentOS glibc Security Update
|glibc-2.17-106.el7_2.4.i686.rpm, glibc-2.17-106.el7_2.4.src.rpm, glibc-2.17-106.el7_2.4.x86_64.rpm, glibc-common-2.17-106.el7_2.4.x86_64.rpm, glibc-devel-2.17-106.el7_2.4.i686.rpm, glibc-devel-2.17-106.el7_2.4.x86_64.rpm, glibc-headers-2.17-106.el7_2.4.x86_64.rpm, glibc-static-2.17-106.el7_2.4.i686.rpm, glibc-static-2.17-106.el7_2.4.x86_64.rpm, glibc-utils-2.17-106.el7_2.4.x86_64.rpm, nscd-2.17-106.el7_2.4.x86_64.rpm|
Updated glibc packages that fix two security issues and two bugs are now
available for Red Hat Enterprise Linux 7.
Red Hat Product Security has rated this update as having Critical security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.
The glibc packages provide the standard C libraries (libc), POSIX
thread libraries (libpthread), standard math libraries (libm), and the
name service cache daemon (nscd) used by multiple programs on the
system. Without these libraries, the Linux system cannot function
A stack-based buffer overflow was found in the way the libresolv library
performed dual A/AAAA DNS queries. A remote attacker could create a
specially crafted DNS response which could cause libresolv to crash or,
potentially, execute code with the permissions of the user running the
library. Note: this issue is only exposed when libresolv is called from the
nss_dns NSS service module. (CVE-2015-7547)
It was discovered that the calloc implementation in glibc could return
memory areas which contain non-zero bytes. This could result in unexpected
application behavior such as hangs or crashes. (CVE-2015-5229)
The CVE-2015-7547 issue was discovered by the Google Security Team and Red
Hat. Red Hat would like to thank Jeff Layton for reporting the
This update also fixes the following bugs:
* The existing implementation of the "free" function causes all memory
pools beyond the first to return freed memory directly to the operating
system as quickly as possible. This can result in performance degradation
when the rate of free calls is very high. The first memory pool (the main
pool) does provide a method to rate limit the returns via M_TRIM_THRESHOLD,
but this method is not available to subsequent memory pools.
With this update, the M_TRIM_THRESHOLD method is extended to apply to all
memory pools, which improves performance for threads with very high amounts
of free calls and limits the number of "madvise" system calls. The change
also increases the total transient memory usage by processes because the
trim threshold must be reached before memory can be freed.
To return to the previous behavior, you can either set M_TRIM_THRESHOLD
using the "mallopt" function, or set the MALLOC_TRIM_THRESHOLD environment
variable to 0. (BZ#1298930)
* On the little-endian variant of 64-bit IBM Power Systems (ppc64le), a bug
in the dynamic loader could cause applications compiled with profiling
enabled to fail to start with the error "monstartup: out of memory".
The bug has been corrected and applications compiled for profiling now
start correctly. (BZ#1298956)
All glibc users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues.
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Affected package information