krb5 commit [krb5-1.13]: Fix unaligned accesses in bt_split.c

[Tom Yu]

https://github.com/krb5/krb5/commit/95f4a7da460a2b72c60070f291b7dfbdafd0356c
commit 95f4a7da460a2b72c60070f291b7dfbdafd0356c
Author: Tom Yu <tlyu at mit.edu>
Date:   Wed Sep 7 17:28:34 2016 -0400

    Fix unaligned accesses in bt_split.c
    
    In the libdb2 btree back end, splitting a page at an overflow key
    could result in an unaligned access, causing a crash (and data
    corruption) on platforms with strict alignment.  This probably occurs
    only rarely in practice.
    
    (cherry picked from commit 537aba0dda3a1f696f10fde56348fde06d88939c)
    
    ticket: 8493
    version_fixed: 1.13.7

 src/plugins/kdb/db2/libdb2/btree/bt_split.c |   18 ++++++++++++------
 1 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/plugins/kdb/db2/libdb2/btree/bt_split.c b/src/plugins/kdb/db2/libdb2/btree/bt_split.c
index 2460aa5..c5f151d 100644
--- a/src/plugins/kdb/db2/libdb2/btree/bt_split.c
+++ b/src/plugins/kdb/db2/libdb2/btree/bt_split.c
@@ -245,9 +245,12 @@ __bt_split(t, sp, key, data, flags, ilen, argskip)
 			WR_BINTERNAL(dest, nksize ? nksize : bl->ksize,
 			    rchild->pgno, bl->flags & P_BIGKEY);
 			memmove(dest, bl->bytes, nksize ? nksize : bl->ksize);
-			if (bl->flags & P_BIGKEY &&
-			    bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
-				goto err1;
+			if (bl->flags & P_BIGKEY) {
+				db_pgno_t pgno;
+				memcpy(&pgno, bl->bytes, sizeof(pgno));
+				if (bt_preserve(t, pgno) == RET_ERROR)
+					goto err1;
+			}
 			break;
 		case P_RINTERNAL:
 			/*
@@ -568,9 +571,12 @@ bt_broot(t, h, l, r)
 		 * If the key is on an overflow page, mark the overflow chain
 		 * so it isn't deleted when the leaf copy of the key is deleted.
 		 */
-		if (bl->flags & P_BIGKEY &&
-		    bt_preserve(t, *(db_pgno_t *)bl->bytes) == RET_ERROR)
-			return (RET_ERROR);
+		if (bl->flags & P_BIGKEY) {
+			db_pgno_t pgno;
+			memcpy(&pgno, bl->bytes, sizeof(pgno));
+			if (bt_preserve(t, pgno) == RET_ERROR)
+				return (RET_ERROR);
+		}
 		break;
 	case P_BINTERNAL:
 		bi = GETBINTERNAL(r, 0);