From 1da951c4c3b4e403a6c1668a54e6264381c0003d Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Tue, 8 Feb 2022 15:48:04 -0500
Subject: [PATCH 1/3] virtiofsd: Fix breakage due to fuse_init_in size change

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-MergeRequest: 193: virtiofsd: Fix breakage due to fuse_init_in size change
RH-Commit: [1/1] 5809db034f9361fb462181d71e7cdde1324f8e54
RH-Bugzilla: 2097209
RH-Acked-by: German Maglione <None>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Vivek Goyal <None>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

Kernel version 5.17 has increased the size of "struct fuse_init_in" struct.
Previously this struct was 16 bytes and now it has been extended to
64 bytes in size.

Once qemu headers are updated to latest, it will expect to receive 64 byte
size struct (for protocol version major 7 and minor > 6). But if guest is
booting older kernel (older than 5.17), then it still sends older
fuse_init_in of size 16 bytes. And do_init() fails. It is expecting
64 byte struct. And this results in mount of virtiofs failing.

Fix this by parsing 16 bytes only for now. Separate patches will be
posted which will parse rest of the bytes and enable new functionality.
Right now we don't support any of the new functionality, so we don't
lose anything by not parsing bytes beyond 16.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Message-Id: <20220208204813.682906-2-vgoyal@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit a086d54c6ffa38f7e71f182b63a25315304a3392)
---
 tools/virtiofsd/fuse_lowlevel.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowlevel.c
index e4679c73ab..5d431a7038 100644
--- a/tools/virtiofsd/fuse_lowlevel.c
+++ b/tools/virtiofsd/fuse_lowlevel.c
@@ -1880,6 +1880,8 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid,
                     struct fuse_mbuf_iter *iter)
 {
     size_t compat_size = offsetof(struct fuse_init_in, max_readahead);
+    size_t compat2_size = offsetof(struct fuse_init_in, flags) +
+                              sizeof(uint32_t);
     struct fuse_init_in *arg;
     struct fuse_init_out outarg;
     struct fuse_session *se = req->se;
@@ -1897,7 +1899,7 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid,
 
     /* ...and now consume the new fields. */
     if (arg->major == 7 && arg->minor >= 6) {
-        if (!fuse_mbuf_iter_advance(iter, sizeof(*arg) - compat_size)) {
+        if (!fuse_mbuf_iter_advance(iter, compat2_size - compat_size)) {
             fuse_reply_err(req, EINVAL);
             return;
         }
-- 
2.35.3