From 5fa91c573b9502e84c037cddf770753d7d337b96 Mon Sep 17 00:00:00 2001
From: Alexander Boettcher <alexander.boettcher@genode-labs.com>
Date: Wed, 20 Jan 2021 09:16:27 +0100
Subject: [PATCH] libc: update O_APPEND fds on joined child

The fds in O_APPEND state may have changed by the child. The local seek
state needs to be valid/current for the next to be forked child, which seek
state is set by File_descriptor_allocator::generate_info().

Issue #3991
---
 repos/libports/include/libc-plugin/fd_alloc.h |  5 +++++
 repos/libports/src/lib/libc/fd_alloc.cc       | 11 +++++++++++
 repos/libports/src/lib/libc/fork.cc           |  2 ++
 3 files changed, 18 insertions(+)

diff --git a/repos/libports/include/libc-plugin/fd_alloc.h b/repos/libports/include/libc-plugin/fd_alloc.h
index 33bbcec2fe..4be81b0917 100644
--- a/repos/libports/include/libc-plugin/fd_alloc.h
+++ b/repos/libports/include/libc-plugin/fd_alloc.h
@@ -113,6 +113,11 @@ namespace Libc {
 			 */
 			File_descriptor *any_cloexec_libc_fd();
 
+			/**
+			 * Update seek state of file descriptor with append flag set.
+			 */
+			void update_append_libc_fds();
+
 			/**
 			 * Return file-descriptor ID of any open file, or -1 if no file is
 			 * open
diff --git a/repos/libports/src/lib/libc/fd_alloc.cc b/repos/libports/src/lib/libc/fd_alloc.cc
index e6fb4d83da..39de362201 100644
--- a/repos/libports/src/lib/libc/fd_alloc.cc
+++ b/repos/libports/src/lib/libc/fd_alloc.cc
@@ -127,6 +127,17 @@ File_descriptor *File_descriptor_allocator::any_cloexec_libc_fd()
 }
 
 
+void File_descriptor_allocator::update_append_libc_fds()
+{
+	Mutex::Guard guard(_mutex);
+
+	_id_space.for_each<File_descriptor>([&] (File_descriptor &fd) {
+		if (fd.flags & O_APPEND)
+			fd.plugin->lseek(&fd, 0, SEEK_END);
+	});
+}
+
+
 int File_descriptor_allocator::any_open_fd()
 {
 	Mutex::Guard guard(_mutex);
diff --git a/repos/libports/src/lib/libc/fork.cc b/repos/libports/src/lib/libc/fork.cc
index e4f0c7fb5a..eb434659b5 100644
--- a/repos/libports/src/lib/libc/fork.cc
+++ b/repos/libports/src/lib/libc/fork.cc
@@ -721,6 +721,8 @@ extern "C" pid_t __sys_wait4(pid_t pid, int *status, int options, rusage *rusage
 		return Fn::INCOMPLETE;
 	});
 
+	file_descriptor_allocator()->update_append_libc_fds();
+
 	/*
 	 * The libc expects status information in bits 0..6 and the exit value
 	 * in bits 8..15 (according to 'wait.h').