From 4604df9ada906e0a6537157a63b6ce7c0509f34d Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Thu, 28 Jan 2021 06:08:38 +0000
Subject: [PATCH] Stack robustness fixes from OpenSUSE
Three OpenSUSE patches from:
https://build.opensuse.org/package/show/shells/ksh
As usual, the relevant bug is not currently public:
https://bugzilla.opensuse.org/show_bug.cgi?id=844071
src/cmd/ksh93/sh/xec.c: sh_debug()/sh_exec():
- Fix stk restoration. [bnc#844071]
src/lib/libast/misc/stk.c:
- Fix stk aliasing code. [bnc#844071]
(ksh93-stkalias.dif)
- Make a unknown location fatal in stkset() so that we get a core
dump right away instead of later in an unrelated part of code.
(ksh93-stkset-abort.dif)
src/lib/libast/man/stk.3,
src/lib/libast/man/stak.3:
- Update manual with new stkset() behaviour. (93u+m addition)
(Note that stak is implemented as macros that translate to stk)
---
src/cmd/ksh93/sh/xec.c | 6 +++---
src/lib/libast/man/stak.3 | 5 +++--
src/lib/libast/man/stk.3 | 5 +++--
src/lib/libast/misc/stk.c | 16 ++++++++++------
4 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/src/cmd/ksh93/sh/xec.c b/src/cmd/ksh93/sh/xec.c
index 23526098ec20..ca3876394d63 100644
--- a/src/cmd/ksh93/sh/xec.c
+++ b/src/cmd/ksh93/sh/xec.c
@@ -646,8 +646,8 @@ int sh_debug(Shell_t *shp, const char *trap, const char *name, const char *subsc
Stk_t *stkp=shp->stk;
struct sh_scoped savst;
Namval_t *np = SH_COMMANDNOD;
- char *sav = stkptr(stkp,0);
int n=4, offset=stktell(stkp);
+ char *sav = stkfreeze(stkp,0);
const char *cp = "+=( ";
Sfio_t *iop = stkstd;
short level;
@@ -702,7 +702,7 @@ int sh_debug(Shell_t *shp, const char *trap, const char *name, const char *subsc
nv_putval(SH_FUNNAMENOD,shp->st.funname,NV_NOFREE);
shp->st = savst;
if(sav != stkptr(stkp,0))
- stkset(stkp,sav,0);
+ stkset(stkp,sav,offset);
else
stkseek(stkp,offset);
return(n);
@@ -962,7 +962,7 @@ int sh_exec(register const Shnode_t *t, int flags)
int ntflag = 0;
#endif
int topfd = shp->topfd;
- char *sav=stkptr(stkp,0);
+ char *sav=stkfreeze(stkp,0);
char *cp=0, **com=0, *comn;
int argn;
int skipexitset = 0;
diff --git a/src/lib/libast/man/stak.3 b/src/lib/libast/man/stak.3
index 5feac69..89e0f54 100644
--- a/src/lib/libast/man/stak.3
+++ b/src/lib/libast/man/stak.3
@@ -109,8 +109,9 @@ the given \fIaddress\fP, and sets the current object to the given
\fIaddress\fP.
The top of the current object is set to \fIoffset\fP bytes from
current object.
-If \fIaddress\fP is not the address of an object on the
-stack the result is undefined.
+If \fIaddress\fP is null, the stack is reset to the beginning.
+If it is non-null, but is not the address of an object on the
+stack, the program aborts and dumps core.
.PP
The remaining functions are used to build the current object incrementally.
An object that is built incrementally on the stack will
diff --git a/src/lib/libast/man/stk.3 b/src/lib/libast/man/stk.3
index 20dfdbefa44c..dd5705cf1188 100644
--- a/src/lib/libast/man/stk.3
+++ b/src/lib/libast/man/stk.3
@@ -110,8 +110,9 @@ the given \fIaddress\fP, and sets the current object to the given
\fIaddress\fP.
The top of the current object is set to \fIoffset\fP bytes from
current object.
-If \fIaddress\fP is not the address of an object on the
-stack the result is undefined.
+If \fIaddress\fP is null, the stack is reset to the beginning.
+If it is non-null, but is not the address of an object on the
+stack, the program aborts and dumps core.
.PP
The \f5sfio\fP(3) output functions can be used to build
current object incrementally.
diff --git a/src/lib/libast/misc/stk.c b/src/lib/libast/misc/stk.c
index 31cd0911dd29..f147ae4fec8c 100644
--- a/src/lib/libast/misc/stk.c
+++ b/src/lib/libast/misc/stk.c
@@ -331,9 +331,9 @@ int stkon(register Sfio_t * stream, register char* loc)
}
/*
* reset the bottom of the current stack back to <loc>
- * if <loc> is not in this stack, then the stack is reset to the beginning
+ * if <loc> is null, then the stack is reset to the beginning
+ * if <loc> is not in this stack, the program dumps core
* otherwise, the top of the stack is set to stkbot+<offset>
- *
*/
char *stkset(register Sfio_t * stream, register char* loc, size_t offset)
{
@@ -377,6 +377,9 @@ char *stkset(register Sfio_t * stream, register char* loc, size_t offset)
break;
frames++;
}
+ /* not found: produce a useful stack trace now instead of a useless one later */
+ if(loc)
+ abort();
/* set stack back to the beginning */
cp = (char*)(fp+1);
if(frames)
@@ -503,7 +506,7 @@ static char *stkgrow(register Sfio_t *stream, size_t size)
register char *cp, *dp=0;
register size_t m = stktell(stream);
size_t endoff;
- char *end=0;
+ char *end=0, *oldbase=0;
int nn=0,add=1;
n += (m + sizeof(struct frame)+1);
if(sp->stkflags&STK_SMALL)
@@ -519,6 +522,7 @@ static char *stkgrow(register Sfio_t *stream, size_t size)
dp=sp->stkbase;
sp->stkbase = ((struct frame*)dp)->prev;
end = fp->end;
+ oldbase = dp;
}
endoff = end - dp;
cp = newof(dp, char, n, nn*sizeof(char*));
@@ -545,10 +549,10 @@ static char *stkgrow(register Sfio_t *stream, size_t size)
if(fp->nalias=nn)
{
fp->aliases = (char**)fp->end;
- if(end && nn>1)
- memmove(fp->aliases,end,(nn-1)*sizeof(char*));
+ if(end && nn>add)
+ memmove(fp->aliases,end,(nn-add)*sizeof(char*));
if(add)
- fp->aliases[nn-1] = dp + roundof(sizeof(struct frame),STK_ALIGN);
+ fp->aliases[nn-1] = oldbase + roundof(sizeof(struct frame),STK_ALIGN);
}
if(m && !dp)
{