[PATCH] Cygwin: sched_setaffinity: fix EACCES if pid of other process is used

[Christian Franke]

This fixes:

$ taskset -p 0x1 1234
pid 1234's current affinity mask: fffffff
taskset: failed to set pid 1234's affinity: Permission denied

Perhaps older Windows versions were more relaxed if 
PROCESS_SET_INFORMATION is granted.

-- 
Regards,
Christian

-------------- next part --------------
From 0275a36723dd4552a26880e4ac8ba9b6dc41b17f Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.franke@t-online.de>
Date: Sat, 8 Mar 2025 14:05:20 +0100
Subject: [PATCH] Cygwin: sched_setaffinity: fix EACCES if pid of other process
 is used

GetProcessGroupAffinity() requires PROCESS_QUERY_LIMITED_INFORMATION.

Fixes: 641ecb07533e ("Cygwin: Implement sched_[gs]etaffinity()")
Signed-off-by: Christian Franke <christian.franke@t-online.de>
---
 winsup/cygwin/release/3.6.0 | 2 ++
 winsup/cygwin/sched.cc      | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/release/3.6.0 b/winsup/cygwin/release/3.6.0
index 8225f2ccc..4c953a84d 100644
--- a/winsup/cygwin/release/3.6.0
+++ b/winsup/cygwin/release/3.6.0
@@ -126,3 +126,5 @@ Fixes:
 
 - Fix 'lost connection' error in scp.
   Addresses: https://cygwin.com/pipermail/cygwin/2025-January/257143.html
+
+- Fix EACCES error of sched_setaffinity(2) if pid of other process is used.
diff --git a/winsup/cygwin/sched.cc b/winsup/cygwin/sched.cc
index 86941b2ac..2f4fbc31a 100644
--- a/winsup/cygwin/sched.cc
+++ b/winsup/cygwin/sched.cc
@@ -661,7 +661,8 @@ sched_setaffinity (pid_t pid, size_t sizeof_set, const cpu_set_t *set)
   if (p)
     {
       process = pid && pid != myself->pid ?
-		OpenProcess (PROCESS_SET_INFORMATION, FALSE,
+		OpenProcess (PROCESS_SET_INFORMATION |
+			     PROCESS_QUERY_LIMITED_INFORMATION, FALSE,
 			     p->dwProcessId) : GetCurrentProcess ();
       if (!GetProcessGroupAffinity (process, &groupcount, grouparray))
 	{
-- 
2.45.1