Messages in this thread Patch in this message | | | Date | Tue, 22 Nov 2022 09:21:43 +0900 | From | Dominique Martinet <> | Subject | Re: [PATCH 2/2] net/9p: fix response size check in p9_check_errors() |
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Christian Schoenebeck wrote on Tue, Nov 22, 2022 at 12:04:08AM +0100: > Since 60ece0833b6c (net/9p: allocate appropriate reduced message buffers) > it is no longer appropriate to check server's response size against > msize. Check against the previously allocated buffer capacity instead.
Thanks for the follow up!
> - Omit this size check entirely for zero-copy messages, as those always > allocate 4k (P9_ZC_HDR_SZ) linear buffers which are not used for actual > payload and can be much bigger than 4k.
[review includes the new flag patch]
hmm, unless there's anywhere else you think we might use these flags it looks simpler to just pass a flag to p9_check_errors?
In particular adding a bool in this position is not particularly efficient: -------(pahole)----- struct p9_fcall { u32 size; /* 0 4 */ u8 id; /* 4 1 */
/* XXX 1 byte hole, try to pack */
u16 tag; /* 6 2 */ size_t offset; /* 8 8 */ size_t capacity; /* 16 8 */ bool zc; /* 24 1 */
/* XXX 7 bytes hole, try to pack */
struct kmem_cache * cache; /* 32 8 */ u8 * sdata; /* 40 8 */
/* size: 48, cachelines: 1, members: 8 */ /* sum members: 40, holes: 2, sum holes: 8 */ /* last cacheline: 48 bytes */ }; ---------------- Not that adding it between id and tag sounds better to me, so this is probably just as good as anywhere else :-D
Anyway, I'm just nitpicking -- on principle I agree just whitelisting zc requests from this check makes most sense, happy with either way if you think this is better for the future.
> - Replace p9_debug() by pr_err() to make sure this message is always > printed in case this error is triggered. > > - Add 9p message type to error message to ease investigation.
Yes to these log changes!
> > Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com> > --- > net/9p/client.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/net/9p/client.c b/net/9p/client.c > index 30dd82f49b28..63f13dd1ecff 100644 > --- a/net/9p/client.c > +++ b/net/9p/client.c > @@ -514,10 +514,10 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req) > int ecode; > > err = p9_parse_header(&req->rc, NULL, &type, NULL, 0); > - if (req->rc.size >= c->msize) { > - p9_debug(P9_DEBUG_ERROR, > - "requested packet size too big: %d\n", > - req->rc.size); > + if (req->rc.size > req->rc.capacity && !req->rc.zc) { > + pr_err( > + "requested packet size too big: %d does not fit %ld (type=%d)\n", > + req->rc.size, req->rc.capacity, req->rc.id);
Haven't seen this style before -- is that what qemu uses? We normally keep the message on first line and align e.g. > + pr_err("requested packet size too big: %d does not fit %ld (type=%d)\n", > + req->rc.size, req->rc.capacity, req->rc.id);
(at least what's what other grep -A 1 'pr_err.*,$' seem to do, and checkpatch is happier with that)
-- Dominique
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