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ash: refresh stack pointers after makestrspace in rmescapes

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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 <uberlord@gentoo.org>.  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 <cjwatson@ubuntu.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Colin Watson 2010-04-26 14:21:27 +02:00 committed by Denys Vlasenko
parent 920185c69a
commit 3963d943f8
1 changed files with 4 additions and 0 deletions
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4
shell/ash.c
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@ -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);
/* p and str may be invalidated by makestrspace */
str = (char *)stackblock() + strloc;
p = str + len;
} else if (flag & RMESCAPE_HEAP) {
r = ckmalloc(fulllen);
} else {