libsa: Fix infinite loop in bzipfs & gzipfs

A bug in the loader's bzipfs & gzipfs filesystems caused compressed
kernel and modules not to work on EFI systems with a veriexec-enabled
loader. Since the size of files in these filesystems are not known
_a priori_ `stat` would initialize the size to -1 and the loader would
then hang in an infinite loop while trying to seek (read) to the end
of file since the loop termination condition compares the current
offset to that negative target position.

Sponsored by:	Dell EMC Isilon

(cherry picked from commit 3df4c387d2e3ca4c2391fb837540b048f60a11c2)

2 files changed, 6 insertions, 0 deletions

diff --git a/stand/libsa/bzipfs.c b/stand/libsa/bzipfs.c
index 47380ae72e5e..bb67bda2aa19 100644
--- a/stand/libsa/bzipfs.c
+++ b/stand/libsa/bzipfs.c
@@ -340,6 +340,9 @@ bzf_seek(struct open_file *f, off_t offset, int where)
 	    target - bzf->bzf_bzstream.total_out_lo32), NULL);
 	if (errno)
 	    return(-1);
+	/* Break out of loop if end of file has been reached. */
+	if (bzf->bzf_endseen)
+	    break;
     }
     /* This is where we are (be honest if we overshot) */
     return(bzf->bzf_bzstream.total_out_lo32);
diff --git a/stand/libsa/gzipfs.c b/stand/libsa/gzipfs.c
index 39e2f98eb1e0..8154b0f95a9a 100644
--- a/stand/libsa/gzipfs.c
+++ b/stand/libsa/gzipfs.c
@@ -315,6 +315,9 @@ zf_seek(struct open_file *f, off_t offset, int where)
 	    target - zf->zf_zstream.total_out), NULL);
 	if (errno)
 	    return(-1);
+	/* Break out of loop if end of file has been reached. */
+	if (zf->zf_endseen)
+	    break;
     }
     /* This is where we are (be honest if we overshot) */
     return(zf->zf_zstream.total_out);