Re: [Feature Request?] Inline compression of process core dumps

[Alan Cox]

> Looking at the code, it seems to me that format_corename() is appending 
> .pid, regardless if !core_uses_pid and corename[0]=='|', in which case 
> it creates an invalid path for call_usermodehelper_pipe().
> 
> Bug in the code, or bug in my methods?

This looks somewhat better and might do the trick. Also fixes a very very
obscure security corner case. If you change core pattern to start with
the program name then the user can run a program called "|myevilhack" as
it stands. The patch checks for "|" in the pattern not the output and
doesn't nail a pid on to a piped name.

Signed-off-by: Alan Cox <[EMAIL PROTECTED]>

diff -u --exclude-from /usr/src/exclude --new-file --recursive 
linux.vanilla-2.6.21-rc6-mm1/fs/exec.c linux-2.6.21-rc6-mm1/fs/exec.c
--- linux.vanilla-2.6.21-rc6-mm1/fs/exec.c      2007-04-12 14:15:05.000000000 
+0100
+++ linux-2.6.21-rc6-mm1/fs/exec.c      2007-04-13 13:11:20.709835952 +0100
@@ -1265,13 +1265,17 @@
  * name into corename, which must have space for at least
  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
  */
-static void format_corename(char *corename, const char *pattern, long signr)
+static int format_corename(char *corename, const char *pattern, long signr)
 {
        const char *pat_ptr = pattern;
        char *out_ptr = corename;
        char *const out_end = corename + CORENAME_MAX_SIZE;
        int rc;
        int pid_in_pattern = 0;
+       int ispipe = 0;
+       
+       if (*pattern == '|')
+               ispipe = 1;
 
        /* Repeat as long as we have more pattern to process and more output
           space */
@@ -1362,8 +1366,8 @@
         *
         * If core_pattern does not include a %p (as is the default)
         * and core_uses_pid is set, then .%pid will be appended to
-        * the filename */
-       if (!pid_in_pattern
+        * the filename. Do not do this for piped commands. */
+       if (!ispipe && !pid_in_pattern
             && (core_uses_pid || atomic_read(&current->mm->mm_users) != 1)) {
                rc = snprintf(out_ptr, out_end - out_ptr,
                              ".%d", current->tgid);
@@ -1371,8 +1375,9 @@
                        goto out;
                out_ptr += rc;
        }
-      out:
+out:
        *out_ptr = 0;
+       return ispipe;
 }
 
 static void zap_process(struct task_struct *start)
@@ -1523,16 +1528,15 @@
         * uses lock_kernel()
         */
        lock_kernel();
-       format_corename(corename, core_pattern, signr);
+       ispipe = format_corename(corename, core_pattern, signr);
        unlock_kernel();
-       if (corename[0] == '|') {
+       if (ispipe) {
                /* SIGPIPE can happen, but it's just never processed */
                if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) {
                        printk(KERN_INFO "Core dump to %s pipe failed\n",
                               corename);
                        goto fail_unlock;
                }
-               ispipe = 1;
        } else
                file = filp_open(corename,
                                 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
-
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