[PATCH v2 0/2] net/9p: fix response size check in p9_check_errors()

[PATCH v2 0/2] net/9p: fix response size check in p9_check_errors()

[Christian Schoenebeck]

Follow-up fix for:
https://lore.kernel.org/linux-kernel/Y3hADWgV9JeajmfF@codewreck.org/

Dominique, I moved `zc` to the end of the structure to somewhat address
the layout padding. If you prefer a function argument in the first place,
let me know and I'll send a v3.

v1 -> v2:

  * Move `zc` to end of struct p9_rstatf (to avoid huge padding).
    [patch 1]

  * Fix format specifier for `capacity` (reported by kernel test bot).
    [patch 2]

  * Fix code style. [patch 1..2]

  * Extend and adjust commit log messages. [patch 1..2]

Christian Schoenebeck (2):
  net/9p: distinguish zero-copy requests
  net/9p: fix response size check in p9_check_errors()

 include/net/9p/9p.h |  2 ++
 net/9p/client.c     | 13 +++++++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

-- 
2.30.2

[PATCH v2 1/2] net/9p: distinguish zero-copy requests

[Christian Schoenebeck]

Add boolean `zc` member to struct p9_fcall to distinguish zero-copy
messages (not using the linear `sdata` buffer for message payload) from
regular messages (which do copy message payload to `sdata` before being
further processed).

This new member is appended to end of structure to avoid inserting huge
padding in generated layout.

Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
---
 include/net/9p/9p.h | 2 ++
 net/9p/client.c     | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 13abe013af21..429adf6be29c 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -531,6 +531,7 @@ struct p9_rstatfs {
  * @offset: used by marshalling routines to track current position in buffer
  * @capacity: used by marshalling routines to track total malloc'd capacity
  * @sdata: payload
+ * @zc: whether zero-copy is used
  *
  * &p9_fcall represents the structure for all 9P RPC
  * transactions.  Requests are packaged into fcalls, and reponses
@@ -549,6 +550,7 @@ struct p9_fcall {
 
 	struct kmem_cache *cache;
 	u8 *sdata;
+	bool zc;
 };
 
 int p9_errstr2errno(char *errstr, int len);
diff --git a/net/9p/client.c b/net/9p/client.c
index aaa37b07e30a..c7935e392812 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -680,6 +680,9 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 	if (IS_ERR(req))
 		return req;
 
+	req->tc.zc = false;
+	req->rc.zc = false;
+
 	if (signal_pending(current)) {
 		sigpending = 1;
 		clear_thread_flag(TIF_SIGPENDING);
@@ -778,6 +781,9 @@ static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
 	if (IS_ERR(req))
 		return req;
 
+	req->tc.zc = true;
+	req->rc.zc = true;
+
 	if (signal_pending(current)) {
 		sigpending = 1;
 		clear_thread_flag(TIF_SIGPENDING);
-- 
2.30.2

[PATCH v2 2/2] net/9p: fix response size check in p9_check_errors()

[Christian Schoenebeck]

Since commit 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.

- 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.

- 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.

Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
---
 net/9p/client.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index c7935e392812..0ff25c2157ab 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -514,10 +514,9 @@ 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 %zu (type=%d)\n",
+		       req->rc.size, req->rc.capacity, req->rc.id);
 		return -EIO;
 	}
 	/* dump the response from server
-- 
2.30.2