[PATCH] seccomp: fix memory leak on filter attach

[Kees Cook]

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@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 kernel/seccomp.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index fd609bd9d6dd..2d7dcdfb7422 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -256,6 +256,7 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
 		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);
@@ -265,6 +266,7 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
 	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;
-- 
1.7.9.5


-- 
Kees Cook
Chrome OS Security
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