1 files changed, 9 insertions, 1 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 705fe9fa4..90fb00fbd 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6411,7 +6411,15 @@ subevalvar(char *p, char *varname, int strloc, int subtype,
                                 len = number(loc);
                         }
                 }
-                if (pos >= orig_len) {
+                if (pos < 0) {
+                        /* ${VAR:$((-n)):l} starts n chars from the end */
+                        pos = orig_len + pos;
+                }
+                if ((unsigned)pos >= orig_len) {
+                        /* apart from obvious ${VAR:999999:l},
+                         * covers ${VAR:$((-9999999)):l} - result is ""
+                         * (bash-compat)
+                         */
                         pos = 0;
                         len = 0;
                 }