[PATCH libdrm] drm: Avoid out of bound write in drmOpenByName()

[Damien Lespiau]

In the fallback code that looks for devices in /proc, the read() may
return with -1 in case of error (interruption from a signal for
instance). We'll then happily write '\0' to buf[-2].

As we didn't really care about the signal interruption before, I kept it
the same way, just making sure that retcode is > 0 to avoid that case.

This was found by static analysis.

Signed-off-by: Damien Lespiau <damien.lespiau at intel.com>
---
 xf86drm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xf86drm.c b/xf86drm.c
index d900b4b..106b8ab 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -579,7 +579,7 @@ static int drmOpenByName(const char *name)
 	if ((fd = open(proc_name, 0, 0)) >= 0) {
 	    retcode = read(fd, buf, sizeof(buf)-1);
 	    close(fd);
-	    if (retcode) {
+	    if (retcode > 0) {
 		buf[retcode-1] = '\0';
 		for (driver = pt = buf; *pt && *pt != ' '; ++pt)
 		    ;
-- 
1.8.3.1