On Mon, 28 Aug 2023 13:09:18 +0200 Corinna Vinschen wrote: > On Aug 28 12:57, Corinna Vinschen wrote: > > On Aug 28 18:46, Takashi Yano wrote: > > > Previously, the number of command line args was not checked for > > > cygwin process. Due to this, segmentation fault was caused if too > > > many command line args are specified. > > > https://cygwin.com/pipermail/cygwin/2023-August/254333.html > > > > > > Since char *argv[argc + 1] is placed on the stack in dll_crt0_1(), > > > STATUS_STACK_OVERFLOW occurs if the stack does not have enough > > > space. > > > > > > With this patch, the total length of the arguments and the size of > > > argv[] is restricted to 1/4 of total stack size for the process, and > > > spawnve() returns E2BIG if the size exceeds the limit. > > > [...] > > I tried this simple patch: > > > > diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc > > index 49b7a44aeb15..961dea4ab993 100644 > > --- a/winsup/cygwin/dcrt0.cc > > +++ b/winsup/cygwin/dcrt0.cc > > @@ -978,11 +978,8 @@ dll_crt0_1 (void *) > > a change to an element of argv[] it does not affect Cygwin's argv. > > Changing the the contents of what argv[n] points to will still > > affect Cygwin. This is similar (but not exactly like) Linux. */ > > - char *newargv[__argc + 1]; > > - char **nav = newargv; > > - char **oav = __argv; > > - while ((*nav++ = *oav++) != NULL) > > - continue; > > + char **newargv = (char **) malloc ((__argc + 1) * sizeof (char **)); > > + memcpy (newargv, __argv, (__argc + 1) * sizeof (char **)); > > /* Handle any signals which may have arrived */ > > sig_dispatch_pending (false); > > _my_tls.call_signal_handler (); > > > > and the testcase `LC_ALL=C sed 's/x/y/' $(seq 1000000)' simply ran > > as desired. Combined with a bit of error checking... > > We may also get away with storing it in the Windows heap, but I didn't > test this . > > > Along these lines, there's no reason to couple SC_ARG_MAX to the > > size of the stack. I'd propose to return the value 2097152. It's > > the default value returned by getconf ARG_MAX on LInx as well. > > Oh, and we can carefully check in child_info_spawn::worker that > the args are not taking more space than the value returned by > SC_ARG_MAX and return E2BIG if so. We do this when checking the > args for non-Cygwin apps anyway.
As for non-cygwin apps, the check seems to be done in linebuf::fromargv() in winf.cc. Further, dcr0.cc code does not affect to non-cygwin app. So my patch check only for cygwin apps case. -- Takashi Yano <takashi.y...@nifty.ne.jp>
