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-rw-r--r--hw/9pfs/9p.c12
-rw-r--r--hw/9pfs/9p.h11
2 files changed, 23 insertions, 0 deletions
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index b0e445d6bd..c63f549f39 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1363,8 +1363,20 @@ static void coroutine_fn v9fs_version(void *opaque)
s->proto_version = V9FS_PROTO_2000L;
} else {
v9fs_string_sprintf(&version, "unknown");
+ /* skip min. msize check, reporting invalid version has priority */
+ goto marshal;
}
+ if (s->msize < P9_MIN_MSIZE) {
+ err = -EMSGSIZE;
+ error_report(
+ "9pfs: Client requested msize < minimum msize ("
+ stringify(P9_MIN_MSIZE) ") supported by this server."
+ );
+ goto out;
+ }
+
+marshal:
err = pdu_marshal(pdu, offset, "ds", s->msize, &version);
if (err < 0) {
goto out;
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 8d07a0b301..b8f72a3bd9 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -100,6 +100,17 @@ typedef enum P9ProtoVersion {
V9FS_PROTO_2000L = 0x02,
} P9ProtoVersion;
+/**
+ * @brief Minimum message size supported by this 9pfs server.
+ *
+ * A client establishes a session by sending a Tversion request along with a
+ * 'msize' parameter which suggests the server a maximum message size ever to be
+ * used for communication (for both requests and replies) between client and
+ * server during that session. If client suggests a 'msize' smaller than this
+ * value then session is denied by server with an error response.
+ */
+#define P9_MIN_MSIZE 4096
+
#define P9_NOTAG UINT16_MAX
#define P9_NOFID UINT32_MAX
#define P9_MAXWELEM 16