ash,hush: properly handle ${v//pattern/repl} if pattern starts with /

Closes 2695

function                                             old     new   delta
parse_dollar                                         762     790     +28
subevalvar                                          1258    1267      +9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 37/0)               Total: 37 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 03fbbee53..5c431c9ff 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6854,8 +6854,15 @@ subevalvar(char *p, char *varname, int strloc, int subtype,
         if (subtype == VSREPLACE || subtype == VSREPLACEALL) {
                 /* Find '/' and replace with NUL */
                 repl = p;
+                /* The pattern can't be empty.
+                 * IOW: if the first char after "${v//" is a slash,
+                 * it does not terminate the pattern - it's the first char of the pattern:
+                 *  v=/dev/ram; echo ${v////-}  prints -dev-ram (pattern is "/")
+                 *  v=/dev/ram; echo ${v///r/-} prints /dev-am  (pattern is "/r")
+                 */
+                if (*repl == '/')
+                        repl++;
                 for (;;) {
-                        /* Handle escaped slashes, e.g. "${v/\//_}" (they are CTLESC'ed by this point) */
                         if (*repl == '\0') {
                                 repl = NULL;
                                 break;
@@ -6864,6 +6871,7 @@ subevalvar(char *p, char *varname, int strloc, int subtype,
                                 *repl = '\0';
                                 break;
                         }
+                        /* Handle escaped slashes, e.g. "${v/\//_}" (they are CTLESC'ed by this point) */
                         if ((unsigned char)*repl == CTLESC && repl[1])
                                 repl++;
                         repl++;