[PATCH 4.3 021/200] proc: fix -ESRCH error when writing to /proc/$pid/coredump_filter

[Greg Kroah-Hartman]

4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

commit 41a0c249cb8706a2efa1ab3d59466b23a27d0c8b upstream.

Writing to /proc/$pid/coredump_filter always returns -ESRCH because commit
774636e19ed51 ("proc: convert to kstrto*()/kstrto*_from_user()") removed
the setting of ret after the get_proc_task call and incorrectly left it as
-ESRCH.  Instead, return 0 when successful.

Example breakage:

  echo 0 > /proc/self/coredump_filter
  bash: echo: write error: No such process

Fixes: 774636e19ed51 ("proc: convert to kstrto*()/kstrto*_from_user()")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/proc/base.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2484,6 +2484,7 @@ static ssize_t proc_coredump_filter_writ
 	mm = get_task_mm(task);
 	if (!mm)
 		goto out_no_mm;
+	ret = 0;
 
 	for (i = 0, mask = 1; i < MMF_DUMP_FILTER_BITS; i++, mask <<= 1) {
 		if (val & mask)