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Re: [Qemu-devel] [PATCH v2 27/28] 9pfs: local: open2: don't follow symli
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v2 27/28] 9pfs: local: open2: don't follow symlinks |
Date: |
Mon, 27 Feb 2017 13:18:30 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Sun, Feb 26, 2017 at 11:45:09PM +0100, Greg Kurz wrote:
> The local_open2() callback is vulnerable to symlink attacks because it
> calls:
>
> (1) open() which follows symbolic links for all path elements but the
> rightmost one
> (2) local_set_xattr()->setxattr() which follows symbolic links for all
> path elements
> (3) local_set_mapped_file_attr() which calls in turn local_fopen() and
> mkdir(), both functions following symbolic links for all path
> elements but the rightmost one
> (4) local_post_create_passthrough() which calls in turn lchown() and
> chmod(), both functions also following symbolic links
>
> This patch converts local_open2() to rely on opendir_nofollow() and
> mkdirat() to fix (1), as well as local_set_xattrat(),
> local_set_mapped_file_attrat() and local_set_cred_passthrough() to
> fix (2), (3) and (4) respectively. Since local_open2() already opens
> a descriptor to the target file, local_set_cred_passthrough() is
> modified to reuse it instead of opening a new one.
>
> The mapped and mapped-file security modes are supposed to be identical,
> except for the place where credentials and file modes are stored. While
> here, we also make that explicit by sharing the call to openat().
>
> This partly fixes CVE-2016-9602.
>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> v2: - use openat_file()
> - pass dirfd and name to local_set_cred_passthrough()
> ---
> hw/9pfs/9p-local.c | 56
> ++++++++++++++++++----------------------------------
> 1 file changed, 19 insertions(+), 37 deletions(-)
Reviewed-by: Stefan Hajnoczi <address@hidden>
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- [Qemu-devel] [PATCH v2 20/28] 9pfs: local: improve error handling in link op, (continued)
- [Qemu-devel] [PATCH v2 20/28] 9pfs: local: improve error handling in link op, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 21/28] 9pfs: local: link: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 22/28] 9pfs: local: chmod: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 23/28] 9pfs: local: chown: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 24/28] 9pfs: local: symlink: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 25/28] 9pfs: local: mknod: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 26/28] 9pfs: local: mkdir: don't follow symlinks, Greg Kurz, 2017/02/26
- [Qemu-devel] [PATCH v2 27/28] 9pfs: local: open2: don't follow symlinks, Greg Kurz, 2017/02/26
- Re: [Qemu-devel] [PATCH v2 27/28] 9pfs: local: open2: don't follow symlinks,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v2 28/28] 9pfs: local: drop unused code, Greg Kurz, 2017/02/26
- Re: [Qemu-devel] [PATCH v2 00/28] 9pfs: local: fix vulnerability to symlink attacks, Greg Kurz, 2017/02/26
- Re: [Qemu-devel] [PATCH v2 00/28] Series short description, Stefan Hajnoczi, 2017/02/27
- Re: [Qemu-devel] [PATCH v2 00/28] Series short description, Stefan Hajnoczi, 2017/02/27