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>

6 files changed, 28 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++;
diff --git a/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.right b/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.right
new file mode 100644
index 000000000..439dca578
--- /dev/null
+++ b/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.right
@@ -0,0 +1,2 @@
+-dev-ram
+/dev-am
diff --git a/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.tests b/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.tests
new file mode 100755
index 000000000..b83fb8eeb
--- /dev/null
+++ b/shell/ash_test/ash-vars/var_bash_pattern_starting_with_slash.tests
@@ -0,0 +1,3 @@
+v=/dev/ram
+echo ${v////-}
+echo ${v///r/-}
diff --git a/shell/hush.c b/shell/hush.c
index 6852b5f79..3407711cd 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -4930,6 +4930,15 @@ static int parse_dollar(o_string *as_string,
                                         end_ch = '}' * 0x100 + '/';
                                 }
                                 o_addchr(dest, ch);
+                                /* The pattern can't be empty.
+                                 * IOW: if the first char after "${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 (i_peek(input) == '/') {
+                                        o_addchr(dest, i_getch(input));
+                                }
  again:
                                 if (!BB_MMU)
                                         pos = dest->length;
diff --git a/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.right b/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.right
new file mode 100644
index 000000000..439dca578
--- /dev/null
+++ b/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.right
@@ -0,0 +1,2 @@
+-dev-ram
+/dev-am
diff --git a/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.tests b/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.tests
new file mode 100755
index 000000000..b83fb8eeb
--- /dev/null
+++ b/shell/hush_test/hush-vars/var_bash_pattern_starting_with_slash.tests
@@ -0,0 +1,3 @@
+v=/dev/ram
+echo ${v////-}
+echo ${v///r/-}