proc: fix -ESRCH error when writing to /proc/$pid/coredump_filter

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@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org> [4.3+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index bd3e9e68125b8933b2e32a4fea2e2282397dc1cd..4bd5d3118acd4b152d6e6f17b38b0a03b0f723d6 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2494,6 +2494,7 @@ static ssize_t proc_coredump_filter_write(struct file *file,
        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)