fix FS_IOC_{GET,SET}{FLAGS,VERSION} ioctl calls

libfuse/include/fuse.h

@@ -505,8 +505,13 @@ struct fuse_operations {
 	 *
 	 * Introduced in version 2.8
 	 */
-	int (*ioctl) (const char *, int cmd, void *arg,
-		      struct fuse_file_info *, unsigned int flags, void *data);
+	int (*ioctl) (const char *fusepath,
+                      int cmd,
+                      void *arg,
+		      struct fuse_file_info *ffi,
+                      unsigned int flags,
+                      void *data,
+                      uint32_t *out_bufsz);
 
 	/**
 	 * Poll for IO readiness events
@@ -884,7 +889,8 @@ int fuse_fs_removexattr(struct fuse_fs *fs, const char *path,
 int fuse_fs_bmap(struct fuse_fs *fs, const char *path, size_t blocksize,
 		 uint64_t *idx);
 int fuse_fs_ioctl(struct fuse_fs *fs, const char *path, int cmd, void *arg,
-		  struct fuse_file_info *fi, unsigned int flags, void *data);
+		  struct fuse_file_info *fi, unsigned int flags,
+                  void *data, uint32_t *out_bufsz);
 int fuse_fs_poll(struct fuse_fs *fs, const char *path,
 		 struct fuse_file_info *fi, struct fuse_pollhandle *ph,
 		 unsigned *reventsp);

libfuse/lib/fuse.c

@@ -2202,7 +2202,8 @@ int fuse_fs_removexattr(struct fuse_fs *fs, const char *path, const char *name)
 }
 
 int fuse_fs_ioctl(struct fuse_fs *fs, const char *path, int cmd, void *arg,
-		  struct fuse_file_info *fi, unsigned int flags, void *data)
+		  struct fuse_file_info *fi, unsigned int flags,
+                  void *data, uint32_t *out_size)
 {
 	fuse_get_context()->private_data = fs->user_data;
 	if (fs->op.ioctl) {
@@ -2210,7 +2211,7 @@ int fuse_fs_ioctl(struct fuse_fs *fs, const char *path, int cmd, void *arg,
 			fprintf(stderr, "ioctl[%llu] 0x%x flags: 0x%x\n",
 				(unsigned long long) fi->fh, cmd, flags);
 
-		return fs->op.ioctl(path, cmd, arg, fi, flags, data);
+		return fs->op.ioctl(path, cmd, arg, fi, flags, data, out_size);
 	} else
 		return -ENOSYS;
 }
@@ -3896,13 +3897,14 @@ static void fuse_lib_bmap(fuse_req_t req, fuse_ino_t ino, size_t blocksize,
 static void fuse_lib_ioctl(fuse_req_t req, fuse_ino_t ino, int cmd, void *arg,
 			   struct fuse_file_info *llfi, unsigned int flags,
 			   const void *in_buf, size_t in_bufsz,
-			   size_t out_bufsz)
+			   size_t out_bufsz_)
 {
 	struct fuse *f = req_fuse_prepare(req);
 	struct fuse_intr_data d;
 	struct fuse_file_info fi;
 	char *path, *out_buf = NULL;
 	int err;
+        uint32_t out_bufsz = out_bufsz_;
 
 	err = -EPERM;
 	if (flags & FUSE_IOCTL_UNRESTRICTED)
@@ -3931,7 +3933,7 @@ static void fuse_lib_ioctl(fuse_req_t req, fuse_ino_t ino, int cmd, void *arg,
 	fuse_prepare_interrupt(f, req, &d);
 
 	err = fuse_fs_ioctl(f->fs, path, cmd, arg, &fi, flags,
-			    out_buf ?: (void *)in_buf);
+			    out_buf ?: (void *)in_buf, &out_bufsz);
 
 	fuse_finish_interrupt(f, req, &d);
 	free_path(f, ino, path);

src/endian.hpp

@@ -0,0 +1,32 @@
+/*
+  ISC License
+
+  Copyright (c) 2019, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+namespace endian
+{
+  static
+  inline
+  bool
+  is_big(void)
+  {
+    const union { uint32_t i; char c[4]; } u = { 0x01000000 };
+
+    return u.c[0];
+  }
+};

src/fs_base_ioctl.hpp

@@ -22,6 +22,15 @@
 
 namespace fs
 {
+  static
+  inline
+  int
+  ioctl(const int           fd_,
+        const unsigned long request_)
+  {
+    return ::ioctl(fd_,request_);
+  }
+
   static
   inline
   int

src/fuse_ioctl.cpp

@@ -16,6 +16,7 @@
 
 #include "config.hpp"
 #include "dirinfo.hpp"
+#include "endian.hpp"
 #include "errno.hpp"
 #include "fileinfo.hpp"
 #include "fs_base_close.hpp"
@@ -35,17 +36,67 @@
 using std::string;
 using std::vector;
 
+#ifndef FS_IOC_GETFLAGS
+# define FS_IOC_GETFLAGS _IOR('f',1,long)
+#endif
+
+#ifndef FS_IOC_SETFLAGS
+# define FS_IOC_SETFLAGS _IOW('f',2,long)
+#endif
+
+#ifndef FS_IOC_GETVERSION
+# define FS_IOC_GETVERSION _IOR('v',1,long)
+#endif
+
+#ifndef FS_IOC_SETVERSION
+# define FS_IOC_SETVERSION _IOW('v',2,long)
+#endif
+
+/*
+  There is a bug with FUSE and these ioctl commands. The regular
+  libfuse high level API assumes the output buffer size based on the
+  command and gives no control over this. FS_IOC_GETFLAGS and
+  FS_IOC_SETFLAGS however are defined as `long` when in fact it is an
+  `int`. On 64bit systems where long is 8 bytes this can lead to
+  libfuse telling the kernel to write 8 bytes and if the user only
+  allocated an integer then it will overwrite the 4 bytes after the
+  variable which could result in data corruption and/or crashes.
+
+  I've modified the API to allow changing of the output buffer
+  size. This fixes the issue on little endian systems because the
+  lower 4 bytes are the same regardless of what the user
+  allocated. However, on big endian systems thats not the case and it
+  is not possible to safely handle the situation.
+
+  https://lwn.net/Articles/575846/
+ */
+
 namespace l
 {
   static
   int
   ioctl(const int  fd_,
-        const unsigned long  cmd_,
-        void                *data_)
+        const int  cmd_,
+        void      *data_,
+        uint32_t  *out_bufsz_)
   {
     int rv;
 
-    rv = fs::ioctl(fd_,cmd_,data_);
+    switch(cmd_)
+      {
+      case FS_IOC_GETFLAGS:
+      case FS_IOC_SETFLAGS:
+      case FS_IOC_GETVERSION:
+      case FS_IOC_SETVERSION:
+        if(endian::is_big() && (sizeof(long) != sizeof(int)))
+          return -ENOTTY;
+        *out_bufsz_ = 4;
+        break;
+      }
+
+    rv = ((_IOC_DIR(cmd_) == _IOC_NONE) ?
+          fs::ioctl(fd_,cmd_) :
+          fs::ioctl(fd_,cmd_,data_));
 
     return ((rv == -1) ? -errno : rv);
   }
@@ -53,12 +104,13 @@ namespace l
   static
   int
   ioctl_file(fuse_file_info *ffi_,
-             const unsigned long  cmd_,
-             void                *data_)
+             const int       cmd_,
+             void           *data_,
+             uint32_t       *out_bufsz_)
   {
     FileInfo *fi = reinterpret_cast<FileInfo*>(ffi_->fh);
 
-    return l::ioctl(fi->fd,cmd_,data_);
+    return l::ioctl(fi->fd,cmd_,data_,out_bufsz_);
   }
 
 
@@ -72,8 +124,9 @@ namespace l
                  const Branches       &branches_,
                  const uint64_t        minfreespace_,
                  const char           *fusepath_,
-                 const unsigned long   cmd_,
-                 void                 *data_)
+                 const int             cmd_,
+                 void                 *data_,
+                 uint32_t             *out_bufsz_)
   {
     int fd;
     int rv;
@@ -91,7 +144,7 @@ namespace l
     if(fd == -1)
       return -errno;
 
-    rv = l::ioctl(fd,cmd_,data_);
+    rv = l::ioctl(fd,cmd_,data_,out_bufsz_);
 
     fs::close(fd);
 
@@ -101,8 +154,9 @@ namespace l
   static
   int
   ioctl_dir(fuse_file_info *ffi_,
-            const unsigned long  cmd_,
-            void                *data_)
+            const int       cmd_,
+            void           *data_,
+            uint32_t       *out_bufsz_)
   {
     DirInfo                 *di     = reinterpret_cast<DirInfo*>(ffi_->fh);
     const fuse_context      *fc     = fuse_get_context();
@@ -115,7 +169,8 @@ namespace l
                              config.minfreespace,
                              di->fusepath.c_str(),
                              cmd_,
-                             data_);
+                             data_,
+                             out_bufsz_);
   }
 }
 
@@ -127,12 +182,12 @@ namespace FUSE
         void           *arg_,
         fuse_file_info *ffi_,
         unsigned int    flags_,
-        void           *data_)
+        void           *data_,
+        uint32_t       *out_bufsz_)
   {
     if(flags_ & FUSE_IOCTL_DIR)
-      return l::ioctl_dir(ffi_,cmd_,data_);
-
+      return l::ioctl_dir(ffi_,cmd_,data_,out_bufsz_);
 
-    return l::ioctl_file(ffi_,cmd_,data_);
+    return l::ioctl_file(ffi_,cmd_,data_,out_bufsz_);
   }
 }

src/fuse_ioctl.hpp

@@ -26,5 +26,6 @@ namespace FUSE
         void           *arg_,
         fuse_file_info *ffi_,
         unsigned int    flags_,
-        void           *data_);
+        void           *data_,
+        uint32_t       *out_bufsz_);
 }