fuse: fix LOOKUP vs INIT compat handling

Analysis from Marc:

 "Commit 7078187a795f ("fuse: introduce fuse_simple_request() helper")
  from the above pull request triggers some EIO errors for me in some tests
  that rely on fuse

  Looking at the code changes and a bit of debugging info I think there's a
  general problem here that fuse_get_req checks and possibly waits for
  fc->initialized, and this was always called first.  But this commit
  changes the ordering and in many places fc->minor is now possibly used
  before fuse_get_req, and we can't be sure that fc has been initialized.
  In my case fuse_lookup_init sets req->out.args[0].size to the wrong size
  because fc->minor at that point is still 0, leading to the EIO error."

Fix by moving the compat adjustments into fuse_simple_request() to after
fuse_get_req().

This is also more readable than the original, since now compatibility is
handled in a single function instead of cluttering each operation.

Reported-by: Marc Dionne <marc.c.dionne@gmail.com>
Tested-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Fixes: 7078187a795f ("fuse: introduce fuse_simple_request() helper")

3 files changed, 44 insertions, 26 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ba1107977f2e..c847d6b225e2 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -511,6 +511,39 @@ void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
 }
 EXPORT_SYMBOL_GPL(fuse_request_send);
 
+static void fuse_adjust_compat(struct fuse_conn *fc, struct fuse_args *args)
+{
+        if (fc->minor < 4 && args->in.h.opcode == FUSE_STATFS)
+                args->out.args[0].size = FUSE_COMPAT_STATFS_SIZE;
+
+        if (fc->minor < 9) {
+                switch (args->in.h.opcode) {
+                case FUSE_LOOKUP:
+                case FUSE_CREATE:
+                case FUSE_MKNOD:
+                case FUSE_MKDIR:
+                case FUSE_SYMLINK:
+                case FUSE_LINK:
+                        args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+                        break;
+                case FUSE_GETATTR:
+                case FUSE_SETATTR:
+                        args->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+                        break;
+                }
+        }
+        if (fc->minor < 12) {
+                switch (args->in.h.opcode) {
+                case FUSE_CREATE:
+                        args->in.args[0].size = sizeof(struct fuse_open_in);
+                        break;
+                case FUSE_MKNOD:
+                        args->in.args[0].size = FUSE_COMPAT_MKNOD_IN_SIZE;
+                        break;
+                }
+        }
+}
+
 ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
 {
         struct fuse_req *req;
@@ -520,6 +553,9 @@ ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
         if (IS_ERR(req))
                 return PTR_ERR(req);
 
+        /* Needs to be done after fuse_get_req() so that fc->minor is valid */
+        fuse_adjust_compat(fc, args);
+
         req->in.h.opcode = args->in.h.opcode;
         req->in.h.nodeid = args->in.h.nodeid;
         req->in.numargs = args->in.numargs;
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 252b8a5de8b5..08e7b1a9d5d0 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -156,10 +156,7 @@ static void fuse_lookup_init(struct fuse_conn *fc, struct fuse_args *args,
         args->in.args[0].size = name->len + 1;
         args->in.args[0].value = name->name;
         args->out.numargs = 1;
-        if (fc->minor < 9)
-                args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-        else
-                args->out.args[0].size = sizeof(struct fuse_entry_out);
+        args->out.args[0].size = sizeof(struct fuse_entry_out);
         args->out.args[0].value = outarg;
 }
 
@@ -422,16 +419,12 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
         args.in.h.opcode = FUSE_CREATE;
         args.in.h.nodeid = get_node_id(dir);
         args.in.numargs = 2;
-        args.in.args[0].size = fc->minor < 12 ? sizeof(struct fuse_open_in) :
-                                                sizeof(inarg);
+        args.in.args[0].size = sizeof(inarg);
         args.in.args[0].value = &inarg;
         args.in.args[1].size = entry->d_name.len + 1;
         args.in.args[1].value = entry->d_name.name;
         args.out.numargs = 2;
-        if (fc->minor < 9)
-                args.out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-        else
-                args.out.args[0].size = sizeof(outentry);
+        args.out.args[0].size = sizeof(outentry);
         args.out.args[0].value = &outentry;
         args.out.args[1].size = sizeof(outopen);
         args.out.args[1].value = &outopen;
@@ -539,10 +532,7 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_args *args,
         memset(&outarg, 0, sizeof(outarg));
         args->in.h.nodeid = get_node_id(dir);
         args->out.numargs = 1;
-        if (fc->minor < 9)
-                args->out.args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
-        else
-                args->out.args[0].size = sizeof(outarg);
+        args->out.args[0].size = sizeof(outarg);
         args->out.args[0].value = &outarg;
         err = fuse_simple_request(fc, args);
         if (err)
@@ -592,8 +582,7 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
         inarg.umask = current_umask();
         args.in.h.opcode = FUSE_MKNOD;
         args.in.numargs = 2;
-        args.in.args[0].size = fc->minor < 12 ? FUSE_COMPAT_MKNOD_IN_SIZE :
-                                                sizeof(inarg);
+        args.in.args[0].size = sizeof(inarg);
         args.in.args[0].value = &inarg;
         args.in.args[1].size = entry->d_name.len + 1;
         args.in.args[1].value = entry->d_name.name;
@@ -899,10 +888,7 @@ static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
         args.in.args[0].size = sizeof(inarg);
         args.in.args[0].value = &inarg;
         args.out.numargs = 1;
-        if (fc->minor < 9)
-                args.out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
-        else
-                args.out.args[0].size = sizeof(outarg);
+        args.out.args[0].size = sizeof(outarg);
         args.out.args[0].value = &outarg;
         err = fuse_simple_request(fc, &args);
         if (!err) {
@@ -1574,10 +1560,7 @@ static void fuse_setattr_fill(struct fuse_conn *fc, struct fuse_args *args,
         args->in.args[0].size = sizeof(*inarg_p);
         args->in.args[0].value = inarg_p;
         args->out.numargs = 1;
-        if (fc->minor < 9)
-                args->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
-        else
-                args->out.args[0].size = sizeof(*outarg_p);
+        args->out.args[0].size = sizeof(*outarg_p);
         args->out.args[0].value = outarg_p;
 }
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 6749109f255d..6a20f2ff2c2e 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -424,8 +424,7 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
         args.in.h.opcode = FUSE_STATFS;
         args.in.h.nodeid = get_node_id(dentry->d_inode);
         args.out.numargs = 1;
-        args.out.args[0].size =
-                fc->minor < 4 ? FUSE_COMPAT_STATFS_SIZE : sizeof(outarg);
+        args.out.args[0].size = sizeof(outarg);
         args.out.args[0].value = &outarg;
         err = fuse_simple_request(fc, &args);
         if (!err)