linux-user/elfload: Fix pr_pid values in core files

util: Add qemu_close_all_open_fd
 net/tap: Use qemu_close_all_open_fd
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Merge tag 'pull-misc-20240805' of https://gitlab.com/rth7680/qemu into staging

linux-user/elfload: Fix pr_pid values in core files
util: Add qemu_close_all_open_fd
net/tap: Use qemu_close_all_open_fd

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# gpg: Signature made Mon 05 Aug 2024 10:30:35 AM AEST
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [ultimate]

* tag 'pull-misc-20240805' of https://gitlab.com/rth7680/qemu:
  net/tap: Use qemu_close_all_open_fd()
  qemu/osdep: Add excluded fd parameter to qemu_close_all_open_fd()
  net/tap: Factorize fd closing after forking
  qemu/osdep: Split qemu_close_all_open_fd() and add fallback
  qemu/osdep: Move close_all_open_fds() to oslib-posix
  linux-user/elfload: Fix pr_pid values in core files

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/qemu/osdep.h

@@ -757,6 +757,17 @@ static inline void qemu_reset_optind(void)
 
 int qemu_fdatasync(int fd);
 
+/**
+ * qemu_close_all_open_fd:
+ *
+ * Close all open file descriptors except the ones supplied in the @skip array
+ *
+ * @skip: ordered array of distinct file descriptors that should not be closed
+ *        if any, or NULL.
+ * @nskip: number of entries in the @skip array or 0 if @skip is NULL.
+ */
+void qemu_close_all_open_fd(const int *skip, unsigned int nskip);
+
 /**
  * Sync changes made to the memory mapped file back to the backing
  * storage. For POSIX compliant systems this will fallback

linux-user/elfload.c

@@ -4102,8 +4102,7 @@ static void fill_elf_note_phdr(struct elf_phdr *phdr, size_t sz, off_t offset)
     bswap_phdr(phdr, 1);
 }
 
-static void fill_prstatus_note(void *data, const TaskState *ts,
+static void fill_prstatus_note(void *data, CPUState *cpu, int signr)
-                               CPUState *cpu, int signr)
 {
     /*
      * Because note memory is only aligned to 4, and target_elf_prstatus
@@ -4113,7 +4112,7 @@ static void fill_prstatus_note(void *data, const TaskState *ts,
     struct target_elf_prstatus prstatus = {
         .pr_info.si_signo = signr,
         .pr_cursig = signr,
-        .pr_pid = ts->ts_tid,
+        .pr_pid = get_task_state(cpu)->ts_tid,
         .pr_ppid = getppid(),
         .pr_pgrp = getpgrp(),
         .pr_sid = getsid(0),
@@ -4428,8 +4427,7 @@ static int elf_core_dump(int signr, const CPUArchState *env)
         CPU_FOREACH(cpu_iter) {
             dptr = fill_note(&hptr, NT_PRSTATUS, "CORE",
                              sizeof(struct target_elf_prstatus));
-            fill_prstatus_note(dptr, ts, cpu_iter,
+            fill_prstatus_note(dptr, cpu_iter, cpu_iter == cpu ? signr : 0);
-                               cpu_iter == cpu ? signr : 0);
         }
 
         if (dump_write(fd, header, data_offset) < 0) {

net/tap.c

@@ -385,6 +385,24 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
     return s;
 }
 
+static void close_all_fds_after_fork(int excluded_fd)
+{
+    const int skip_fd[] = {STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO,
+                           excluded_fd};
+    unsigned int nskip = ARRAY_SIZE(skip_fd);
+
+    /*
+     * skip_fd must be an ordered array of distinct fds, exclude
+     * excluded_fd if already included in the [STDIN_FILENO - STDERR_FILENO]
+     * range
+     */
+    if (excluded_fd <= STDERR_FILENO) {
+        nskip--;
+    }
+
+    qemu_close_all_open_fd(skip_fd, nskip);
+}
+
 static void launch_script(const char *setup_script, const char *ifname,
                           int fd, Error **errp)
 {
@@ -400,13 +418,7 @@ static void launch_script(const char *setup_script, const char *ifname,
         return;
     }
     if (pid == 0) {
-        int open_max = sysconf(_SC_OPEN_MAX), i;
+        close_all_fds_after_fork(fd);
-
-        for (i = 3; i < open_max; i++) {
-            if (i != fd) {
-                close(i);
-            }
-        }
         parg = args;
         *parg++ = (char *)setup_script;
         *parg++ = (char *)ifname;
@@ -490,17 +502,11 @@ static int net_bridge_run_helper(const char *helper, const char *bridge,
         return -1;
     }
     if (pid == 0) {
-        int open_max = sysconf(_SC_OPEN_MAX), i;
         char *fd_buf = NULL;
         char *br_buf = NULL;
         char *helper_cmd = NULL;
 
-        for (i = 3; i < open_max; i++) {
+        close_all_fds_after_fork(sv[1]);
-            if (i != sv[1]) {
-                close(i);
-            }
-        }
-
         fd_buf = g_strdup_printf("%s%d", "--fd=", sv[1]);
 
         if (strrchr(helper, ' ') || strrchr(helper, '\t')) {

system/async-teardown.c

@@ -26,40 +26,6 @@
 
 static pid_t the_ppid;
 
-/*
- * Close all open file descriptors.
- */
-static void close_all_open_fd(void)
-{
-    struct dirent *de;
-    int fd, dfd;
-    DIR *dir;
-
-#ifdef CONFIG_CLOSE_RANGE
-    int r = close_range(0, ~0U, 0);
-    if (!r) {
-        /* Success, no need to try other ways. */
-        return;
-    }
-#endif
-
-    dir = opendir("/proc/self/fd");
-    if (!dir) {
-        /* If /proc is not mounted, there is nothing that can be done. */
-        return;
-    }
-    /* Avoid closing the directory. */
-    dfd = dirfd(dir);
-
-    for (de = readdir(dir); de; de = readdir(dir)) {
-        fd = atoi(de->d_name);
-        if (fd != dfd) {
-            close(fd);
-        }
-    }
-    closedir(dir);
-}
-
 static void hup_handler(int signal)
 {
     /* Check every second if this process has been reparented. */
@@ -85,9 +51,8 @@ static int async_teardown_fn(void *arg)
     /*
      * Close all file descriptors that might have been inherited from the
      * main qemu process when doing clone, needed to make libvirt happy.
-     * Not using close_range for increased compatibility with older kernels.
      */
-    close_all_open_fd();
+    qemu_close_all_open_fd(NULL, 0);
 
     /* Set up a handler for SIGHUP and unblock SIGHUP. */
     sigaction(SIGHUP, &sa, NULL);

util/oslib-posix.c

@@ -807,3 +807,127 @@ int qemu_msync(void *addr, size_t length, int fd)
 
     return msync(addr, length, MS_SYNC);
 }
+
+static bool qemu_close_all_open_fd_proc(const int *skip, unsigned int nskip)
+{
+    struct dirent *de;
+    int fd, dfd;
+    DIR *dir;
+    unsigned int skip_start = 0, skip_end = nskip;
+
+    dir = opendir("/proc/self/fd");
+    if (!dir) {
+        /* If /proc is not mounted, there is nothing that can be done. */
+        return false;
+    }
+    /* Avoid closing the directory. */
+    dfd = dirfd(dir);
+
+    for (de = readdir(dir); de; de = readdir(dir)) {
+        bool close_fd = true;
+
+        if (de->d_name[0] == '.') {
+            continue;
+        }
+        fd = atoi(de->d_name);
+        if (fd == dfd) {
+            continue;
+        }
+
+        for (unsigned int i = skip_start; i < skip_end; i++) {
+            if (fd < skip[i]) {
+                /* We are below the next skipped fd, break */
+                break;
+            } else if (fd == skip[i]) {
+                close_fd = false;
+                /* Restrict the range as we found fds matching start/end */
+                if (i == skip_start) {
+                    skip_start++;
+                } else if (i == skip_end) {
+                    skip_end--;
+                }
+                break;
+            }
+        }
+
+        if (close_fd) {
+            close(fd);
+        }
+    }
+    closedir(dir);
+
+    return true;
+}
+
+static bool qemu_close_all_open_fd_close_range(const int *skip,
+                                               unsigned int nskip,
+                                               int open_max)
+{
+#ifdef CONFIG_CLOSE_RANGE
+    int max_fd = open_max - 1;
+    int first = 0, last;
+    unsigned int cur_skip = 0;
+    int ret;
+
+    do {
+        /* Find the start boundary of the range to close */
+        while (cur_skip < nskip && first == skip[cur_skip]) {
+            cur_skip++;
+            first++;
+        }
+
+        /* Find the upper boundary of the range to close */
+        last = max_fd;
+        if (cur_skip < nskip) {
+            last = skip[cur_skip] - 1;
+            last = MIN(last, max_fd);
+        }
+
+        /* With the adjustments to the range, we might be done. */
+        if (first > last) {
+            break;
+        }
+
+        ret = close_range(first, last, 0);
+        if (ret < 0) {
+            return false;
+        }
+
+        first = last + 1;
+    } while (last < max_fd);
+
+    return true;
+#else
+    return false;
+#endif
+}
+
+static void qemu_close_all_open_fd_fallback(const int *skip, unsigned int nskip,
+                                            int open_max)
+{
+    unsigned int cur_skip = 0;
+
+    /* Fallback */
+    for (int i = 0; i < open_max; i++) {
+        if (cur_skip < nskip && i == skip[cur_skip]) {
+            cur_skip++;
+            continue;
+        }
+        close(i);
+    }
+}
+
+/*
+ * Close all open file descriptors.
+ */
+void qemu_close_all_open_fd(const int *skip, unsigned int nskip)
+{
+    int open_max = sysconf(_SC_OPEN_MAX);
+
+    assert(skip != NULL || nskip == 0);
+
+    if (!qemu_close_all_open_fd_close_range(skip, nskip, open_max) &&
+        !qemu_close_all_open_fd_proc(skip, nskip)) {
+        qemu_close_all_open_fd_fallback(skip, nskip, open_max);
+    }
+}