QProcess/Unix: update the close-file-descriptors feature with a minimum

So that one can pass a few extra file descriptors to the child while
still closing all the rest.

strace -f of this test showed on Linux:

[pid 117952] dup3(4, 0, 0)              = 0
[pid 117952] dup3(9, 1, 0)              = 1
[pid 117952] dup3(11, 2, 0)             = 2
[pid 117952] close(12)                  = 0
[pid 117952] dup2(100, 3)               = 3
[pid 117952] close_range(4, 2147483647, 0) = 0
[pid 117952] execve("testUnixProcessParameters/testUnixProcessParameters", ["testUnixProcessParameters/testUn"..., "file-descriptors2", "3", "100"], 0x561793dc87d0 /* 120 vars */ <unfinished ...>

Pick-to: 6.6
Change-Id: I3e3bfef633af4130a03afffd175e984bf50b558d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 7cd379f9fd..ea39962b9d 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -669,9 +669,9 @@ static void applyProcessParameters(const QProcess::UnixProcessParameters &params
 
     // Close all file descriptors above stderr.
     // This isn't expected to fail, so we ignore close()'s return value.
-    if (params.flags.testFlag(QProcess::UnixProcessFlag::CloseNonStandardFileDescriptors)) {
+    if (params.flags.testFlag(QProcess::UnixProcessFlag::CloseFileDescriptors)) {
         int r = -1;
-        int fd = STDERR_FILENO + 1;
+        int fd = qMax(STDERR_FILENO + 1, params.lowestFileDescriptorToClose);
 #if QT_CONFIG(close_range)
         // On FreeBSD, this probably won't fail.
         // On Linux, this will fail with ENOSYS before kernel 5.9.