Merge pull request #4881 from RalfJung/setfl

ignore file mode and creation flags in F_SETFL

Author: RalfJung

src/tools/miri/src/shims/unix/fd.rs

@@ -196,7 +196,19 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let [flag] = check_min_vararg_count("fcntl(fd, F_SETFL, ...)", varargs)?;
                 let flag = this.read_scalar(flag)?.to_i32()?;
 
-                fd.set_flags(flag, this)
+                // Ignore flags that never get stored by SETFL.
+                // "File access mode (O_RDONLY, O_WRONLY, O_RDWR) and file
+                // creation flags (i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC)
+                // in arg are ignored."
+                let ignored_flags = this.eval_libc_i32("O_RDONLY")
+                    | this.eval_libc_i32("O_WRONLY")
+                    | this.eval_libc_i32("O_RDWR")
+                    | this.eval_libc_i32("O_CREAT")
+                    | this.eval_libc_i32("O_EXCL")
+                    | this.eval_libc_i32("O_NOCTTY")
+                    | this.eval_libc_i32("O_TRUNC");
+
+                fd.set_flags(flag & !ignored_flags, this)
             }
             cmd if this.tcx.sess.target.os == Os::MacOs
                 && cmd == this.eval_libc_i32("F_FULLFSYNC") =>

src/tools/miri/src/shims/unix/unnamed_socket.rs

@@ -170,12 +170,7 @@ impl FileDescription for AnonSocket {
         mut flag: i32,
         ecx: &mut MiriInterpCx<'tcx>,
     ) -> InterpResult<'tcx, Scalar> {
-        // FIXME: File creation flags should be ignored.
-
         let o_nonblock = ecx.eval_libc_i32("O_NONBLOCK");
-        let o_rdonly = ecx.eval_libc_i32("O_RDONLY");
-        let o_wronly = ecx.eval_libc_i32("O_WRONLY");
-        let o_rdwr = ecx.eval_libc_i32("O_RDWR");
 
         // O_NONBLOCK flag can be set / unset by user.
         if flag & o_nonblock == o_nonblock {
@@ -185,9 +180,6 @@ impl FileDescription for AnonSocket {
             self.is_nonblock.set(false);
         }
 
-        // Ignore all file access mode flags.
-        flag &= !(o_rdonly | o_wronly | o_rdwr);
-
         // Throw error if there is any unsupported flag.
         if flag != 0 {
             throw_unsup_format!(

src/tools/miri/tests/pass-dep/libc/libc-pipe.rs

@@ -148,6 +148,24 @@ fn test_pipe_setfl_getfl() {
         errno_result(unsafe { libc::fcntl(fds[0], libc::F_GETFL) }).unwrap(),
         libc::O_RDONLY
     );
+
+    // Test if ignored flags are indeed ignored.
+    errno_check(unsafe {
+        libc::fcntl(
+            fds[0],
+            libc::F_SETFL,
+            libc::O_RDWR
+                | libc::O_CREAT
+                | libc::O_EXCL
+                | libc::O_NOCTTY
+                | libc::O_TRUNC
+                | libc::O_NONBLOCK,
+        )
+    });
+    assert_eq!(
+        errno_result(unsafe { libc::fcntl(fds[0], libc::F_GETFL) }).unwrap(),
+        libc::O_NONBLOCK | libc::O_RDONLY
+    );
 }
 
 /// Test the behaviour of F_SETFL/F_GETFL when a fd is blocking.