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Re: [Qemu-devel] [PATCH 14/29] 9pfs: local: utimensat: don't follow syml

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH 14/29] 9pfs: local: utimensat: don't follow symlinks
Date: Thu, 23 Feb 2017 14:48:05 +0000
User-agent: Mutt/1.7.1 (2016-10-04)

On Mon, Feb 20, 2017 at 03:41:08PM +0100, Greg Kurz wrote:
> The local_utimensat() callback is vulnerable to symlink attacks because it
> calls qemu_utimens()->utimensat(AT_SYMLINK_NOFOLLOW) which follows symbolic
> links in all path elements but the rightmost one or qemu_utimens()->utimes()
> which follows symbolic links for all path elements.
> This patch converts local_utimensat() to rely on opendir_nofollow() and
> utimensat(AT_SYMLINK_NOFOLLOW) directly instead of using qemu_utimens().
> It is hence assumed that the OS supports utimensat(), i.e. has glibc 2.6
> or higher and linux 2.6.22 or higher, which seems reasonable nowadays.
> This partly fixes CVE-2016-9602.
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/9pfs/9p-local.c |   19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)

Reviewed-by: Stefan Hajnoczi <address@hidden>

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