Clean up some edgecases with posix_spawn usage (#5079)

* Check that the pid matches

* Fixup EINTR check

* Remove extra slashes

* fixup

* fixup

* != 0

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

2 files changed, 66 insertions, 20 deletions

diff --git a/src/bun.js/api/bun/subprocess.zig b/src/bun.js/api/bun/subprocess.zig
index 50bd846ac..5695c15ad 100644
--- a/src/bun.js/api/bun/subprocess.zig
+++ b/src/bun.js/api/bun/subprocess.zig
@@ -1462,25 +1462,61 @@ pub const Subprocess = struct {
             const kernel = @import("../../../analytics.zig").GenerateHeader.GeneratePlatform.kernelVersion();
 
             // pidfd_nonblock only supported in 5.10+
-            const pidfd_flags: u32 = if (!is_sync and kernel.orderWithoutTag(.{ .major = 5, .minor = 10, .patch = 0 }).compare(.gte))
+            var pidfd_flags: u32 = if (!is_sync and kernel.orderWithoutTag(.{ .major = 5, .minor = 10, .patch = 0 }).compare(.gte))
                 std.os.O.NONBLOCK
             else
                 0;
 
-            const fd = std.os.linux.pidfd_open(
-                pid,
+            var rc = std.os.linux.pidfd_open(
+                @intCast(pid),
                 pidfd_flags,
             );
 
-            switch (std.os.linux.getErrno(fd)) {
-                .SUCCESS => break :brk @as(std.os.fd_t, @intCast(fd)),
-                else => |err| {
-                    globalThis.throwValue(bun.sys.Error.fromCode(err, .open).toJSC(globalThis));
-                    var status: u32 = 0;
-                    // ensure we don't leak the child process on error
-                    _ = std.os.linux.waitpid(pid, &status, 0);
-                    return .zero;
-                },
+            while (true) {
+                switch (std.os.linux.getErrno(rc)) {
+                    .SUCCESS => break :brk @as(std.os.fd_t, @intCast(rc)),
+                    .INTR => {
+                        rc = std.os.linux.pidfd_open(
+                            @intCast(pid),
+                            pidfd_flags,
+                        );
+                        continue;
+                    },
+                    else => |err| {
+                        if (err == .INVAL) {
+                            if (pidfd_flags != 0) {
+                                rc = std.os.linux.pidfd_open(
+                                    @intCast(pid),
+                                    0,
+                                );
+                                pidfd_flags = 0;
+                                continue;
+                            }
+                        }
+
+                        const error_instance = brk2: {
+                            if (err == .NOSYS) {
+                                break :brk2 globalThis.createErrorInstance(
+                                    \\"pidfd_open(2)" system call is not supported by your Linux kernel
+                                    \\To fix this error, either:
+                                    \\- Upgrade your Linux kernel to a newer version (current: {})
+                                    \\- Ensure the seccomp filter allows "pidfd_open"
+                                ,
+                                    .{
+                                        kernel.fmt(""),
+                                    },
+                                );
+                            }
+
+                            break :brk2 bun.sys.Error.fromCode(err, .open).toJSC(globalThis);
+                        };
+                        globalThis.throwValue(error_instance);
+                        var status: u32 = 0;
+                        // ensure we don't leak the child process on error
+                        _ = std.os.linux.waitpid(pid, &status, 0);
+                        return .zero;
+                    },
+                }
             }
         };
 
@@ -1682,14 +1718,16 @@ pub const Subprocess = struct {
                 this.waitpid_err = err;
             },
             .result => |result| {
-                if (std.os.W.IFEXITED(result.status)) {
-                    this.exit_code = @as(u8, @truncate(std.os.W.EXITSTATUS(result.status)));
-                }
+                if (result.pid != 0) {
+                    if (std.os.W.IFEXITED(result.status)) {
+                        this.exit_code = @as(u8, @truncate(std.os.W.EXITSTATUS(result.status)));
+                    }
 
-                if (std.os.W.IFSIGNALED(result.status)) {
-                    this.signal_code = @as(SignalCode, @enumFromInt(@as(u8, @truncate(std.os.W.TERMSIG(result.status)))));
-                } else if (std.os.W.IFSTOPPED(result.status)) {
-                    this.signal_code = @as(SignalCode, @enumFromInt(@as(u8, @truncate(std.os.W.STOPSIG(result.status)))));
+                    if (std.os.W.IFSIGNALED(result.status)) {
+                        this.signal_code = @as(SignalCode, @enumFromInt(@as(u8, @truncate(std.os.W.TERMSIG(result.status)))));
+                    } else if (std.os.W.IFSTOPPED(result.status)) {
+                        this.signal_code = @as(SignalCode, @enumFromInt(@as(u8, @truncate(std.os.W.STOPSIG(result.status)))));
+                    }
                 }
 
                 if (!this.hasExited()) {
diff --git a/src/install/install.zig b/src/install/install.zig
index d7113cfe9..bcf33cb53 100644
--- a/src/install/install.zig
+++ b/src/install/install.zig
@@ -1250,7 +1250,15 @@ const PackageInstall = struct {
                             std.os.mkdirat(destination_dir_.dir.fd, entry.path, 0o755) catch {};
                         },
                         .file => {
-                            try std.os.linkat(entry.dir.dir.fd, entry.basename, destination_dir_.dir.fd, entry.path, 0);
+                            std.os.linkat(entry.dir.dir.fd, entry.basename, destination_dir_.dir.fd, entry.path, 0) catch |err| {
+                                if (err != error.PathAlreadyExists) {
+                                    return err;
+                                }
+
+                                std.os.unlinkat(destination_dir_.dir.fd, entry.path, 0) catch {};
+                                try std.os.linkat(entry.dir.dir.fd, entry.basename, destination_dir_.dir.fd, entry.path, 0);
+                            };
+
                             real_file_count += 1;
                         },
                         else => {},