seccomp: fix memory leak on filter attach

This sets the correct error code when final filter memory is unavailable,
and frees the raw filter no matter what.

unreferenced object 0xffff8800d6ea4000 (size 512):
  comm "sshd", pid 278, jiffies 4294898315 (age 46.653s)
  hex dump (first 32 bytes):
    21 00 00 00 04 00 00 00 15 00 01 00 3e 00 00 c0  !...........>...
    06 00 00 00 00 00 00 00 21 00 00 00 00 00 00 00  ........!.......
  backtrace:
    [<ffffffff8151414e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811a3a40>] __kmalloc+0x280/0x320
    [<ffffffff8110842e>] prctl_set_seccomp+0x11e/0x3b0
    [<ffffffff8107bb6b>] SyS_prctl+0x3bb/0x4a0
    [<ffffffff8152ef2d>] system_call_fastpath+0x1a/0x1f
    [<ffffffffffffffff>] 0xffffffffffffffff

Reported-by: Masami Ichikawa <masami256@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Masami Ichikawa <masami256@gmail.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
	kernel/seccomp.c

Change-Id: Ide3c27bf378397f8faf4218e75c31e4b8bc43c4c

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index b7a10048a32c11fb473515d9075ef2b0782a563a..260ff1fce63dbaf792e39ffe49235afc19fcf3a4 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -273,7 +273,23 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
        /* Check and rewrite the fprog for seccomp use */
        ret = seccomp_check_filter(filter->insns, filter->len);
        if (ret)
-               goto fail;
+               goto free_prog;
+
+       /* Allocate a new seccomp_filter */
+       ret = -ENOMEM;
+       filter = kzalloc(sizeof(struct seccomp_filter) +
+                        sizeof(struct sock_filter_int) * new_len,
+                        GFP_KERNEL|__GFP_NOWARN);
+       if (!filter)
+               goto free_prog;
+
+       ret = sk_convert_filter(fp, fprog->len, filter->insnsi, &new_len);
+       if (ret)
+               goto free_filter;
+       kfree(fp);
+
+       atomic_set(&filter->usage, 1);
+       filter->len = new_len;
 
        /*
         * If there is an existing filter, make it the prev and don't drop its