[patch] khttpd doesn't detach from the files of its parent

[Alessandro Rubini]

Hi all.

While looking at kHTTPd (linux-2.4.0-test9) I found what looks like a
bug to me.

The daemon doesn't detach itself from the files structure of the
parent process. Therefore, when it is run as a module, the files
opened by  "insmod" (or whatever loads it) remain open.

Besides "aesthetical" issues, this can be a problem: if a script loads
a module redirecting stderr to a file, the filesystem won't be
unmountable before the module is removed. (I reproduced that).

The proposed patch is trivial, so I may miss some detail.

A sample session follows, then the patch.

/alessandro

rudo.root# ps aux | grep http
root      1828  0.0  0.0     0    0 ?        SW   12:57   0:00 [khttpd manager]
root      1848  0.0  0.0     0    0 ?        SW   12:58   0:00 [khttpd - 0]
root      1849  0.0  0.0     0    0 ?        SW   12:58   0:00 [khttpd - 1]
rudo.root# ls -l /proc/1828/fd
total 48
lrwx------    1 root     root           64 Oct 18 13:17 0 -> /dev/ttyp1
lrwx------    1 root     root           64 Oct 18 13:17 1 -> /dev/ttyp1
lrwx------    1 root     root           64 Oct 18 13:17 2 -> /dev/ttyp1
rudo.root# ls -l /proc/1848/fd
total 48
lrwx------    1 root     root           64 Oct 18 13:17 0 -> /dev/ttyp1
lrwx------    1 root     root           64 Oct 18 13:17 1 -> /dev/ttyp1
lrwx------    1 root     root           64 Oct 18 13:17 2 -> /dev/ttyp1

        then, I tried "insmod khttpd < /dev/ttyS0".

rudo.root# ps aux | grep http
root      2031  0.0  0.0     0    0 ttypc    SW   13:22   0:00 [khttpd manager]
root      2034  0.0  0.0     0    0 ttypc    SW   13:22   0:00 [khttpd - 0]
root      2035  0.0  0.0     0    0 ttypc    SW   13:22   0:00 [khttpd - 1]
rudo.root# ls -l /proc/2034/fd
total 27
lr-x------    1 root     root           64 Oct 18 13:22 0 -> /dev/ttyS0
lrwx------    1 root     root           64 Oct 18 13:22 1 -> /dev/ttypc
lrwx------    1 root     root           64 Oct 18 13:22 2 -> /dev/ttypc

        after applying the patch included below, no file remains open

rudo.root# ps aux | grep http
root      2019  0.0  0.0     0    0 ttypc    SW   13:20   0:00 [khttpd manager]
root      2020  0.0  0.0     0    0 ttypc    SW   13:20   0:00 [khttpd - 0]
root      2021  0.0  0.0     0    0 ttypc    SW   13:20   0:00 [khttpd - 1]
rudo.root# ls -l /proc/2020/fd
total 0
rudo.root#

--- ./net/khttpd/main.c.orig    Wed Oct 18 13:01:29 2000
+++ ./net/khttpd/main.c Wed Oct 18 19:13:01 2000
@@ -195,6 +195,7 @@
 {
        sigset_t tmpsig;
        int waitpid_result;
+       int i;
        
        DECLARE_WAIT_QUEUE_HEAD(WQ);
        
@@ -203,6 +204,10 @@
        lock_kernel();   /* This seems to be required for exit_mm */
        exit_mm(current);
        
+       /* init_module has stdin/stdout/stderr open: close them (ARub) */
+       for (i=255; i>=0; i--)
+               if (current->files->fd[i])
+                       close(i);
 
        /* Block all signals except SIGKILL and SIGSTOP */
        spin_lock_irq(&current->sigmask_lock);
@@ -383,7 +388,7 @@
 
        StartSysctl();
        
-       (void)kernel_thread(ManagementDaemon,NULL, CLONE_FS | CLONE_FILES | 
CLONE_SIGHAND);
+       (void)kernel_thread(ManagementDaemon,NULL, CLONE_FS | CLONE_SIGHAND);
        
        return 0;
 }
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
Please read the FAQ at http://www.tux.org/lkml/