cluster/ec: fix selinux issues with mmap()

EC uses mmap() to create a memory area for the dynamic code. Since
the code is created on the fly and executed when needed, this region
of memory needs to have write and execution privileges.

This combination is not allowed by default by selinux. To solve the
problem a file is used as a backend storage for the dynamic code and
it's mapped into two distinct memory regions, one with write access
and the other one with execution access. This approach is the
recommended way to create dynamic code by a program in a more secure
way, and selinux allows it.

Additionally selinux requires that the backend file be stored in a
directory marked with type bin_t to be able to map it in an executable
area. To satisfy this condition, GLUSTERFS_LIBEXECDIR has been used.

This fix also changes the error check for mmap(), that was done
incorrectly (it checked against NULL instead of MAP_FAILED), and it
also correctly propagates the error codes and makes sure they aren't
silently ignored.

> Change-Id: I71c2f88be4e4d795b6cfff96ab3799c362c54291
> BUG: 1402661
> Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
> Reviewed-on: https://review.gluster.org/16405
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Jeff Darcy <jdarcy@redhat.com>

Change-Id: I5c2dd51b1161505316c8f78b73e9a585d0c115d0
BUG: 1418650
Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-on: https://review.gluster.org/16522
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/xlators/cluster/ec/src/ec-inode-read.c b/xlators/cluster/ec/src/ec-inode-read.c
index 6752b675273..775b2baa043 100644
--- a/xlators/cluster/ec/src/ec-inode-read.c
+++ b/xlators/cluster/ec/src/ec-inode-read.c
@@ -1186,7 +1186,11 @@ int32_t ec_readv_rebuild(ec_t * ec, ec_fop_data_t * fop, ec_cbk_data_t * cbk)
             goto out;
         }
 
-        ec_method_decode(&ec->matrix, fsize, cbk->mask, values, blocks, ptr);
+        err = ec_method_decode(&ec->matrix, fsize, cbk->mask, values, blocks,
+                               ptr);
+        if (err != 0) {
+            goto out;
+        }
 
         vector[0].iov_base = ptr + fop->head;
         vector[0].iov_len = size - fop->head;