Fix flaky sysctl completion by handling /proc/sys race conditions

Ignore ENOENT errors during /proc/sys traversal as entries can disappear
between directory enumeration and file access. Continue logging other
errors for investigation.

Fixes: #27252

Signed-off-by: Jan Rodák <[email protected]>

Author: Honny1

cmd/podman/common/completion.go

@@ -2,6 +2,7 @@ package common
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io/fs"
 	"net"
@@ -22,6 +23,7 @@ import (
 	systemdDefine "github.com/containers/podman/v5/pkg/systemd/define"
 	"github.com/containers/podman/v5/pkg/util"
 	securejoin "github.com/cyphar/filepath-securejoin"
+	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	libimageDefine "go.podman.io/common/libimage/define"
 	"go.podman.io/common/libnetwork/types"
@@ -1981,6 +1983,13 @@ func AutocompleteSysctl(_ *cobra.Command, _ []string, toComplete string) ([]stri
 
 	err := filepath.Walk(sysPath, func(path string, info os.FileInfo, err error) error {
 		if err != nil {
+			// /proc/sys is a volatile virtual filesystem whose contents can change rapidly.
+			// Handle race conditions where entries disappear between directory enumeration
+			// and file access attempts - this is expected behavior in busy CI environments.
+			// See: https://github.com/containers/podman/issues/27252
+			if errors.Is(err, fs.ErrNotExist) {
+				return nil
+			}
 			return err
 		}
 
@@ -2000,6 +2009,7 @@ func AutocompleteSysctl(_ *cobra.Command, _ []string, toComplete string) ([]stri
 	})
 
 	if err != nil {
+		logrus.Errorf("failed to scan sysctl parameters in %q: %v", sysPath, err)
 		return nil, cobra.ShellCompDirectiveError
 	}