From: Rich Felker <dalias@aerifal.cx>
Date: Tue, 5 Mar 2019 16:02:15 +0000 (-0500)
Subject: don't reject unknown/future flags in sigaltstack, allow SS_AUTODISARM
X-Git-Tag: v1.1.22~42
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=4918b7fb0d9f3d3fd4b46be3313901fbd772064b;p=oweals%2Fmusl.git

don't reject unknown/future flags in sigaltstack, allow SS_AUTODISARM

historically, and likely accidentally, sigaltstack was specified to
fail with EINVAL if any flag bit other than SS_DISABLE was set. the
resolution of Austin Group issue 1187 fixes this so that the
requirement is only to fail for SS_ONSTACK (which cannot be set) or
"invalid" flags.

Linux fails on the kernel side for invalid flags, but historically
accepts SS_ONSTACK as a no-op, so it needs to be rejected in userspace
still.

with this change, the Linux-specific SS_AUTODISARM, provided since
commit 9680e1d03a794b0e0d5815c749478228ed40a36d but unusable due to
rejection at runtime, is now usable.
---

diff --git a/src/signal/sigaltstack.c b/src/signal/sigaltstack.c
index 62cb81ad..cfa3f5c1 100644
--- a/src/signal/sigaltstack.c
+++ b/src/signal/sigaltstack.c
@@ -9,7 +9,7 @@ int sigaltstack(const stack_t *restrict ss, stack_t *restrict old)
 			errno = ENOMEM;
 			return -1;
 		}
-		if (ss->ss_flags & ~SS_DISABLE) {
+		if (ss->ss_flags & SS_ONSTACK) {
 			errno = EINVAL;
 			return -1;
 		}