On Wed, Jun 25, 2014 at 04:50:51PM -0400, Jeff Moyer wrote:
>
> From: Benjamin LaHaise <bcrl@xxxxxxxxx>
>
> A kernel memory disclosure was introduced in aio_read_events_ring() in v3.10
> by commit a31ad380bed817aa25f8830ad23e1a0480fef797. The changes made to
> aio_read_events_ring() failed to correctly limit the index into
> ctx->ring_pages[], allowing an attacked to cause the subsequent kmap() of
> an arbitrary page with a copy_to_user() to copy the contents into userspace.
> This vulnerability has been assigned CVE-2014-0206. Thanks to Mateusz and
> Petr for disclosing this issue.
>
> [jmoyer@xxxxxxxxxx: backported to 3.10]
> Signed-off-by: Benjamin LaHaise <bcrl@xxxxxxxxx>
> Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
> Cc: Mateusz Guzik <mguzik@xxxxxxxxxx>
> Cc: Petr Matousek <pmatouse@xxxxxxxxxx>
> Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> aio.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index e66b948..872fd26 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -717,6 +717,8 @@ static long aio_read_events_ring(struct kioctx *ctx,
> if (head == ctx->tail)
> goto out;
>
> + head %= ctx->nr_events;
> +
> while (ret < nr) {
> long avail;
> struct io_event *ev;
Hmm. Are you sure it's safe to clamp head but not ctx->tail? The body
of the loop still has:
avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
Seems to me that a better backport would be to bring in the chunks of
the patch that introduce a local on stack tail and clamp that to match
the current code.
commit 5ffac122dbda89fbb29885f35a5d47b0edb8936d
Author: Kent Overstreet <koverstreet@xxxxxxxxxx>
Date: Thu May 9 15:36:07 2013 -0700
aio: Don't use ctx->tail unnecessarily
- z
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