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Re-enable SHOPT_DEVFD, fixing process substitution fd leaks (#218)

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This commit fixes a long-standing bug (present since at least
ksh93r) that caused a file descriptor leak when passing a process
substitution to a function, or (if compiled with SHOPT_SPAWN) to a
nonexistent command.

The leaks only occurred when ksh was compiled with SHOPT_DEVFD; the
FIFO method was unaffected.

src/cmd/ksh93/sh/xec.c: sh_exec():
- When a process substitution is passed to a built-in, the
  remaining file descriptor is closed with sh_iorestore. Do the
  same thing when passing a process substitution to a function.
  This is done by delaying the sh_iorestore() call to 'setexit:'
  where both built-ins and functions terminate and set the exit
  status ($?).
  This means that call now will not be executed if a longjmp is
  done, e.g. due to an error in a special built-in. However, there
  is already another sh_iorestore() call in main.c, exfile(), line
  418, that handles that scenario.
- sh_ntfork() can fail, so rather than assume it will succeed,
  handle a failure by closing extra file descriptors with
  sh_iorestore(). This fixes the leak on command not found with
  SHOPT_SPAWN.

src/cmd/ksh93/include/defs.h:
- Since the file descriptor leaks are now fixed, remove the
  workaround that forced ksh to use the FIFO method.

src/cmd/ksh93/SHOPT.sh:
- Add SHOPT_DEVFD as a configurable option (default: probe).

src/cmd/ksh93/tests/io.sh:
- Add a regression test for the 'not found' file descriptor leak.
- Add a test to ensure it keeps working with 'command'.

Fixes: https://github.com/ksh93/ksh/issues/67
This commit is contained in:
Johnothan King 2021-03-13 05:46:42 -08:00 • committed by GitHub
parent d2c1700f63
commit 6d63b57dd3
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
7 changed files with 35 additions and 17 deletions
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2
src/cmd/ksh93/sh/args.c
View file

@ -758,7 +758,7 @@ struct argnod *sh_argprocsub(Shell_t *shp,struct argnod *argp)
job.jobcontrol = savejobcontrol;
sh_setstate(savestates);
#if SHOPT_DEVFD
close(pv[1-fd]);
sh_close(pv[1-fd]);
sh_iosave(shp,-pv[fd], shp->topfd, (char*)0);
#else
/* remember the FIFO for cleanup in case the command never opens it (see fifo_cleanup(), xec.c) */

15
src/cmd/ksh93/sh/xec.c
View file

@ -1014,7 +1014,7 @@ int sh_exec(register const Shnode_t *t, int flags)
char *trap;
Namval_t *np, *nq, *last_table;
struct ionod *io;
int command=0, flgs=NV_ASSIGN;
int command=0, flgs=NV_ASSIGN, jmpval=0;
shp->bltindata.invariant = type>>(COMBITS+2);
type &= (COMMSK|COMSCAN);
sh_stats(STAT_SCMDS);
@ -1258,7 +1258,7 @@ int sh_exec(register const Shnode_t *t, int flags)
volatile int scope=0, share=0;
volatile void *save_ptr;
volatile void *save_data;
int jmpval, save_prompt;
int save_prompt;
int was_nofork = execflg?sh_isstate(SH_NOFORK):0;
struct checkpt *buffp = (struct checkpt*)stkalloc(shp->stk,sizeof(struct checkpt));
#if SHOPT_VSH
@ -1440,10 +1440,6 @@ int sh_exec(register const Shnode_t *t, int flags)
sh_unscope(shp);
bp->ptr = (void*)save_ptr;
bp->data = (void*)save_data;
/* don't restore for 'exec' or 'redirect' in subshell */
if((shp->topfd>topfd) && !(shp->subshell && (np==SYSEXEC || np==SYSREDIR)))
sh_iorestore(shp,topfd,jmpval);
shp->redir0 = 0;
if(jmpval)
siglongjmp(*shp->jmplist,jmpval);
@ -1456,7 +1452,6 @@ int sh_exec(register const Shnode_t *t, int flags)
if(!command && np && nv_isattr(np,NV_FUNCTION))
{
volatile int indx;
int jmpval=0;
struct checkpt *buffp = (struct checkpt*)stkalloc(shp->stk,sizeof(struct checkpt));
#if SHOPT_NAMESPACE
Namval_t node, *namespace=0;
@ -1557,6 +1552,8 @@ int sh_exec(register const Shnode_t *t, int flags)
#if !SHOPT_DEVFD
fifo_cleanup();
#endif
if(shp->topfd > topfd && !(shp->subshell && (np==SYSEXEC || np==SYSREDIR)))
sh_iorestore(shp,topfd,jmpval);
exitset();
break;
}
@ -1631,6 +1628,10 @@ int sh_exec(register const Shnode_t *t, int flags)
# endif /* _lib_fork */
if(parent<0)
{
/* prevent a file descriptor leak from a 'not found' error */
if(shp->topfd > topfd)
sh_iorestore(shp,topfd,0);
if(shp->comsub==1 && usepipe && unpipe)
sh_iounpipe(shp);
break;