Messages in this thread Patch in this message |  | | | Date | Sun, 10 Feb 2008 13:22:50 +0100 | | From | Bastian Blank <> | | Subject | Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit |
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On Sun, Feb 10, 2008 at 04:40:53AM -0500, Niki Denev wrote: > this fixed the problem for me (kernel 2.6.24.1) : > It appears that the initial patch checked the input to vmsplice_to_user, > but the exploit used vmsplice_to_pipe which remained open to the attack.
This patch is broken. It opens the old hole again.
> @@ -1450,6 +1454,31 @@ > .ops = &user_page_pipe_buf_ops, > }; > > + error = ret = 0; > + > + /* > + * Get user address base and length for this iovec. > + */ > + error = get_user(base, &iov->iov_base); > + if (unlikely(error)) > + return error; > + error = get_user(len, &iov->iov_len); > + if (unlikely(error)) > + return error;
iov is unchecked.
> + if (unlikely(!access_ok(VERIFY_WRITE, base, len))) { > + return -EFAULT; > + }
Use VERIFY_READ and this only checks the first entry.
I checked the following patch and it at least fixes the known exploit.
diff --git a/fs/splice.c b/fs/splice.c index 14e2262..80beb2b 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1237,6 +1237,11 @@ static int get_iovec_page_array(const struct iovec __user *iov, if (unlikely(!base)) break; + if (!access_ok(VERIFY_READ, base, len)) { + error = -EFAULT; + break; + } + /* * Get this base offset and number of pages, then map * in the user pages. -- Even historians fail to learn from history -- they repeat the same mistakes. -- John Gill, "Patterns of Force", stardate 2534.7
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