Mike Frysinger 21f042c804 posix_spawn: use a larger min stack for -fstack-check [BZ #21253] ... When glibc is built with -fstack-check, trying to use posix_spawn can lead to segfaults due to gcc internally probing stack memory too far. The new spawn API will allocate a minimum of 1 page, but the stack checking logic might probe a couple of pages. When it tries to walk them, everything falls apart. The gcc internal docs [1] state the default interval checking is one page. Which means we need two pages (the current one, and the next probed). No target currently defines it larger. Further, it mentions that the default minimum stack size needed to recover from an overflow is 4/8KiB for sjlj or 8/12KiB for others. But some Linux targets (like mips and ppc) go up to 16KiB (and some non-Linux targets go up to 24KiB). Let's create each child with a minimum of 32KiB slack space to support them all, and give us future breathing room. No test is added as existing ones crash. Even a simple call is enough to trigger the problem: char *argv[] = { "/bin/ls", NULL }; posix_spawn(NULL, "/bin/ls", NULL, NULL, argv, NULL); [1] https://gcc.gnu.org/onlinedocs/gcc-6.3.0/gccint/Stack-Checking.html		2017-04-03 15:15:41 -04:00
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linux	posix_spawn: use a larger min stack for -fstack-check [BZ #21253]	2017-04-03 15:15:41 -04:00