Without this, _rmescapes sometimes returns random garbage while
performing parameter expansions such as ${foo#bar}, in the event that
the allocation of r happens to need to reallocate the stack and hence
invalidate str and p. I'd love to provide a test case but unfortunately
it's dependent on exact stack layout, so I don't have anything simpler
than the situation described in
https://bugs.launchpad.net/ubuntu/+source/partman-base/+bug/527401/comments/23
which involved a sequence of foo="${foo#*, }" expansions on a long
string inside our RAID configuration tool.
The same fix has been in dash since 2007-09-26, contributed by Roy
Marples <[email protected]>. I actually came up with it independently
almost to the character, but then synced it up with the variable naming
used in dash when I noticed that change afterwards.
Signed-off-by: Colin Watson <[email protected]>
---
shell/ash.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/shell/ash.c b/shell/ash.c
index 9d55f89..9c85773 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -5425,7 +5425,11 @@ rmescapes(char *str, int flag)
size_t fulllen = len + strlen(p) + 1;
if (flag & RMESCAPE_GROW) {
+ int strloc = str - (char *)stackblock();
+
r = makestrspace(fulllen, expdest);
+ str = (char *)stackblock() + strloc;
+ p = str + len;
} else if (flag & RMESCAPE_HEAP) {
r = ckmalloc(fulllen);
} else {
--
1.7.0.4
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