[PATCH] CIFS: fix use-after-free of the lease keys

[PATCH] CIFS: fix use-after-free of the lease keys

[Aurelien Aptel]

The request buffers are freed right before copying the pointers.
Use the func args instead which are identical and still valid.

Simple reproducer (requires KASAN enabled) on a cifs mount:

echo foo > foo ; tail -f foo & rm foo

Cc: <stable@vger.kernel.org> # 4.20
Fixes: 179e44d49c2f ("smb3: add tracepoint for sending lease break responses to server")
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
---
 fs/cifs/smb2pdu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 846e605175bf..54181387a770 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -4435,8 +4435,8 @@ SMB2_lease_break(const unsigned int xid, struct cifs_tcon *tcon,
 	rc = cifs_send_recv(xid, ses, &rqst, &resp_buf_type, flags, &rsp_iov);
 	cifs_small_buf_release(req);
 
-	please_key_low = (__u64 *)req->LeaseKey;
-	please_key_high = (__u64 *)(req->LeaseKey+8);
+	please_key_low = (__u64 *)lease_key;
+	please_key_high = (__u64 *)(lease_key+8);
 	if (rc) {
 		cifs_stats_fail_inc(tcon, SMB2_OPLOCK_BREAK_HE);
 		trace_smb3_lease_err(le32_to_cpu(lease_state), tcon->tid,
-- 
2.16.4

Re: [PATCH] CIFS: fix use-after-free of the lease keys

[Paulo Alcantara]

Aurelien Aptel <aaptel@suse.com> writes:

> The request buffers are freed right before copying the pointers.
> Use the func args instead which are identical and still valid.
>
> Simple reproducer (requires KASAN enabled) on a cifs mount:
>
> echo foo > foo ; tail -f foo & rm foo
>
> Cc: <stable@vger.kernel.org> # 4.20
> Fixes: 179e44d49c2f ("smb3: add tracepoint for sending lease break responses to server")
> Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> ---
>  fs/cifs/smb2pdu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 846e605175bf..54181387a770 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -4435,8 +4435,8 @@ SMB2_lease_break(const unsigned int xid, struct cifs_tcon *tcon,
>  	rc = cifs_send_recv(xid, ses, &rqst, &resp_buf_type, flags, &rsp_iov);
>  	cifs_small_buf_release(req);
>  
> -	please_key_low = (__u64 *)req->LeaseKey;
> -	please_key_high = (__u64 *)(req->LeaseKey+8);
> +	please_key_low = (__u64 *)lease_key;
> +	please_key_high = (__u64 *)(lease_key+8);
>  	if (rc) {
>  		cifs_stats_fail_inc(tcon, SMB2_OPLOCK_BREAK_HE);
>  		trace_smb3_lease_err(le32_to_cpu(lease_state), tcon->tid,
> -- 
> 2.16.4

Reviewed-by: Paulo Alcantara <palcantara@suse.de>

Thanks!
Paulo

Re: [PATCH] CIFS: fix use-after-free of the lease keys

[Steve French]

Moved into cifs-2.6.git for-next

On Thu, Jan 31, 2019 at 6:53 AM Paulo Alcantara <paulo@paulo.ac> wrote:
>
> Aurelien Aptel <aaptel@suse.com> writes:
>
> > The request buffers are freed right before copying the pointers.
> > Use the func args instead which are identical and still valid.
> >
> > Simple reproducer (requires KASAN enabled) on a cifs mount:
> >
> > echo foo > foo ; tail -f foo & rm foo
> >
> > Cc: <stable@vger.kernel.org> # 4.20
> > Fixes: 179e44d49c2f ("smb3: add tracepoint for sending lease break responses to server")
> > Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> > ---
> >  fs/cifs/smb2pdu.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> > index 846e605175bf..54181387a770 100644
> > --- a/fs/cifs/smb2pdu.c
> > +++ b/fs/cifs/smb2pdu.c
> > @@ -4435,8 +4435,8 @@ SMB2_lease_break(const unsigned int xid, struct cifs_tcon *tcon,
> >       rc = cifs_send_recv(xid, ses, &rqst, &resp_buf_type, flags, &rsp_iov);
> >       cifs_small_buf_release(req);
> >
> > -     please_key_low = (__u64 *)req->LeaseKey;
> > -     please_key_high = (__u64 *)(req->LeaseKey+8);
> > +     please_key_low = (__u64 *)lease_key;
> > +     please_key_high = (__u64 *)(lease_key+8);
> >       if (rc) {
> >               cifs_stats_fail_inc(tcon, SMB2_OPLOCK_BREAK_HE);
> >               trace_smb3_lease_err(le32_to_cpu(lease_state), tcon->tid,
> > --
> > 2.16.4
>
> Reviewed-by: Paulo Alcantara <palcantara@suse.de>
>
> Thanks!
> Paulo



-- 
Thanks,

Steve