Re: [PATCH 4/5] smb: client: Clear sensitive stack data in smb1encrypt.c

[Namjae Jeon]

On Tue, Aug 18, 2026 at 3:33 PM Thomas Huth <thuth@xxxxxxxxxx> wrote:
>
> On 18/08/2026 07.58, Namjae Jeon wrote:
> > On Wed, Aug 12, 2026 at 10:13 PM Thomas Huth <thuth@xxxxxxxxxx> wrote:
> >>
> >> From: Thomas Huth <thuth@xxxxxxxxxx>
> >>
> >> Make sure to not leak signature data via the stack, clear it
> >> with memzero_explicit() before leaving the function.
> >>
> >> To avoid that we have to introduce "goto"-cleanup here, we re-arrange
> >> the code a little bit (and drop the commented cifs_dump_mem debug
> >> code that looks like a leftover from very early days).
> >>
> >> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
> >> ---
> >>   fs/smb/client/smb1encrypt.c | 19 +++++++++----------
> >>   1 file changed, 9 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/fs/smb/client/smb1encrypt.c b/fs/smb/client/smb1encrypt.c
> >> index bf10fdeeedcab..c9eb68f04e7b0 100644
> >> --- a/fs/smb/client/smb1encrypt.c
> >> +++ b/fs/smb/client/smb1encrypt.c
> >> @@ -81,6 +81,7 @@ int cifs_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server,
> >>          else
> >>                  memcpy(cifs_pdu->Signature.SecuritySignature, smb_signature, 8);
> >>
> >> +       memzero_explicit(smb_signature, sizeof(smb_signature));
> >>          return rc;
> >>   }
> >>
> >> @@ -126,15 +127,13 @@ int cifs_verify_signature(struct smb_rqst *rqst,
> >>          rc = cifs_calc_signature(rqst, server, what_we_think_sig_should_be);
> >>          cifs_server_unlock(server);
> > The MD5 context in  cifs_calc_signature()  may remain uncleared when
> > __cifs_calc_signature()  fails.
> >
> > rc = __cifs_calc_signature(...);
> >                                                 ┃
> > memzero_explicit(&ctx, sizeof(ctx));
> My plan was to handle that via a __cleanup() function, too, but I need to
> get that merged first:
>
>   https://lore.kernel.org/lkml/20260813134953.979481-7-thuth@xxxxxxxxxx/
Okay.
Thanks.