Re: [Qemu-devel] [PATCH v2 09/28] 9pfs: local: lsetxattr: don't follow symlinks

[Stefan Hajnoczi]

On Sun, Feb 26, 2017 at 11:42:43PM +0100, Greg Kurz wrote:
> The local_lsetxattr() callback is vulnerable to symlink attacks because
> it calls lsetxattr() which follows symbolic links in all path elements but
> the rightmost one.
> 
> This patch introduces a helper to emulate the non-existing fsetxattrat()
> function: it is implemented with /proc/self/fd which provides a trusted
> path that can be safely passed to lsetxattr().
> 
> local_lsetxattr() is converted to use this helper and opendir_nofollow().
> 
> This partly fixes CVE-2016-9602.
> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> v2: - introduce /proc based fsetxattrat_nofollow()
> ---
>  hw/9pfs/9p-posix-acl.c  |   18 ++++--------------
>  hw/9pfs/9p-util.h       |    2 ++
>  hw/9pfs/9p-xattr-user.c |    8 +-------
>  hw/9pfs/9p-xattr.c      |   39 +++++++++++++++++++++++++++++++++------
>  hw/9pfs/9p-xattr.h      |    3 +++
>  5 files changed, 43 insertions(+), 27 deletions(-)

Reviewed-by: Stefan Hajnoczi <address@hidden>

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