Quoting "J. Bruce Fields" <bfields@xxxxxxxxxxxx>:
On Tue, Oct 24, 2017 at 02:18:52PM -0400, Jeff Layton wrote:
On Tue, 2017-10-24 at 13:53 -0400, J. Bruce Fields wrote:
> 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.
>
Not necessarily. If panic_on_oops is set (and it usually is in
"production" setups), it'll crash the box there.
Maybe they're getting what they asked for?
> The failures look unlikely. (Except for that read_u32... return, I
> wonder if we're missing a check there.)
Agreed, looks like you only hit an error if the read attempts to go out
of bounds. In principle that shouldn't ever happen (and I haven't seen
any reports of it).
Still...I agree with Dros that it's better to handle this without
oopsing if we can. We can return an error from either of those
functions. A sane error and a WARN_ONCE would be better here.
OK, OK, OK.
There are also some more BUGs that could use looking into if anyone
wants to.
--b.
commit eb754930662f
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date: Tue Oct 24 14:58:11 2017 -0400
rpc: remove some BUG()s
It would be kinder to WARN() and recover in several spots here instead
of BUG()ing.
Also, it looks like the read_u32_from_xdr_buf() call could actually
fail, though it might require a broken (or malicious) client, so convert
that to just an error return.
Reported-by: Weston Andros Adamson <dros@xxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c
b/net/sunrpc/auth_gss/svcauth_gss.c
index 7b1ee5a0b03c..73165e9ca5bf 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -855,11 +855,13 @@ 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();
+ if (xdr_buf_subsegment(buf, &integ_buf, 0, integ_len)) {
+ WARN_ON_ONCE(1);
+ return stat;
+ }
/* copy out mic... */
if (read_u32_from_xdr_buf(buf, integ_len, &mic.len))
- BUG();
+ return stat;
if (mic.len > RPC_MAX_AUTH_SIZE)
return stat;
mic.data = kmalloc(mic.len, GFP_KERNEL);
@@ -1611,8 +1613,10 @@ 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();
+ if (xdr_buf_subsegment(resbuf, &integ_buf, integ_offset, integ_len)) {
+ WARN_ON_ONCE(1);
+ goto out_err;
+ }
if (resbuf->tail[0].iov_base == NULL) {
if (resbuf->head[0].iov_len + RPC_MAX_AUTH_SIZE > PAGE_SIZE)
goto out_err;
What about the following BUG() at net/sunrpc/svc_xprt.c:1058:
/*
* Remove a dead transport
*/
static void svc_delete_xprt(struct svc_xprt *xprt)
{
struct svc_serv *serv = xprt->xpt_server;
struct svc_deferred_req *dr;
/* Only do this once */
if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags))
BUG();
dprintk("svc: svc_delete_xprt(%p)\n", xprt);
xprt->xpt_ops->xpo_detach(xprt);
spin_lock_bh(&serv->sv_lock);
list_del_init(&xprt->xpt_list);
WARN_ON_ONCE(!list_empty(&xprt->xpt_ready));
if (test_bit(XPT_TEMP, &xprt->xpt_flags))
serv->sv_tmpcnt--;
spin_unlock_bh(&serv->sv_lock);
while ((dr = svc_deferred_dequeue(xprt)) != NULL)
kfree(dr);
call_xpt_users(xprt);
svc_xprt_put(xprt);
}
I'm suspicious about that comment above the _if_ condition: /* Only do
this once */
Would it help to replace that BUG with a WARN_ON_ONCE?
Thanks
--
Gustavo A. R. Silva
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