linux-kernel - Re: [PATCH] net: sunrpc: svcauth_gss: use BUG_ON instead of if condition followed by BUG

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Date:   Tue, 24 Oct 2017 13:53:42 -0400
From:   "J. Bruce Fields" <bfields@...ldses.org>
To:     Weston Andros Adamson <dros@...key.org>
Cc:     "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Jeff Layton <jlayton@...chiereds.net>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-nfs list <linux-nfs@...r.kernel.org>,
        netdev@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: sunrpc: svcauth_gss: use BUG_ON instead of if
 condition followed by BUG

On Tue, Oct 24, 2017 at 01:26:49PM -0400, Weston Andros Adamson wrote:
> Is there a reason to BUG() in these places? Couldn't we WARN_ON_ONCE and return an error?

I think the BUG() will just kill an nfsd thread that isn't holding any
interesting locks.

The failures look unlikely.  (Except for that read_u32... return, I
wonder if we're missing a check there.)

--b.

> 
> -dros
> 
> > On Oct 23, 2017, at 4:31 PM, J. Bruce Fields <bfields@...ldses.org> wrote:
> > 
> > In the past we've avoided BUG_ON(X) where X might have side effects, on
> > the theory that it should actually be OK just to compile out BUG_ON()s.
> > Has that changed?
> > 
> > In any case, I don't find that this improves readability; dropping.
> > 
> > --b.
> > 
> > On Mon, Oct 23, 2017 at 01:16:35PM -0500, Gustavo A. R. Silva wrote:
> >> Use BUG_ON instead of if condition followed by BUG.
> >> 
> >> This issue was detected with the help of Coccinelle.
> >> 
> >> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
> >> ---
> >> net/sunrpc/auth_gss/svcauth_gss.c | 9 +++------
> >> 1 file changed, 3 insertions(+), 6 deletions(-)
> >> 
> >> diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
> >> index 7b1ee5a..a10ce43 100644
> >> --- a/net/sunrpc/auth_gss/svcauth_gss.c
> >> +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> >> @@ -855,11 +855,9 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct g
> >> 		return stat;
> >> 	if (integ_len > buf->len)
> >> 		return stat;
> >> -	if (xdr_buf_subsegment(buf, &integ_buf, 0, integ_len))
> >> -		BUG();
> >> +	BUG_ON(xdr_buf_subsegment(buf, &integ_buf, 0, integ_len));
> >> 	/* copy out mic... */
> >> -	if (read_u32_from_xdr_buf(buf, integ_len, &mic.len))
> >> -		BUG();
> >> +	BUG_ON(read_u32_from_xdr_buf(buf, integ_len, &mic.len));
> >> 	if (mic.len > RPC_MAX_AUTH_SIZE)
> >> 		return stat;
> >> 	mic.data = kmalloc(mic.len, GFP_KERNEL);
> >> @@ -1611,8 +1609,7 @@ svcauth_gss_wrap_resp_integ(struct svc_rqst *rqstp)
> >> 	BUG_ON(integ_len % 4);
> >> 	*p++ = htonl(integ_len);
> >> 	*p++ = htonl(gc->gc_seq);
> >> -	if (xdr_buf_subsegment(resbuf, &integ_buf, integ_offset, integ_len))
> >> -		BUG();
> >> +	BUG_ON(xdr_buf_subsegment(resbuf, &integ_buf, integ_offset, integ_len));
> >> 	if (resbuf->tail[0].iov_base == NULL) {
> >> 		if (resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE > PAGE_SIZE)
> >> 			goto out_err;
> >> -- 
> >> 2.7.4
> > --
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