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Subject[patch 18/33] exec.c: fix coredump to pipe problem and obscure "security hole"
-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
exec.c: fix coredump to pipe problem and obscure "security hole"

The patch checks for "|" in the pattern not the output and doesn't nail a
pid on to a piped name (as it is a program name not a file)
Also fixes a very very obscure security corner case. If you happen to have
decided on a core pattern that starts with the program name then the user
can run a program called "|myevilhack" as it stands. I doubt anyone does
this.
Signed-off-by: Alan Cox <alan@redhat.com>
Confirmed-by: Christopher S. Aker <caker@theshore.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/exec.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1246,13 +1246,17 @@ EXPORT_SYMBOL(set_binfmt);
* 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 */
@@ -1343,8 +1347,8 @@ static void format_corename(char *corena
*
* 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);
@@ -1352,8 +1356,9 @@ static void format_corename(char *corena
goto out;
out_ptr += rc;
}
- out:
+out:
*out_ptr = 0;
+ return ispipe;
}

static void zap_process(struct task_struct *start)
@@ -1504,16 +1509,15 @@ int do_coredump(long signr, int exit_cod
* 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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